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#include <compare>
 
namespace std {
 // pointer Traits
 template<class Ptr>
 struct pointer_traits; // freestanding
 template<class T>
 struct pointer_traits<T*>; // freestanding
 
 // pointer conversion
 template<class T>
 constexpr T* to_address(T* p) noexcept; // freestanding
 template<class Ptr>
 constexpr auto to_address(const Ptr& p) noexcept; // freestanding
 
 // pointer alignment
 void* align(size_t alignment, size_t size, void*& ptr, size_t& space); // freestanding
 template<size_t N, class T>
 constexpr T* assume_aligned(T* ptr); // freestanding
 template<size_t Alignment, class T>
 bool is_sufficiently_aligned(T* ptr);
 
 // explicit lifetime management
 template<class T>
 T* start_lifetime_as(void* p) noexcept; // freestanding
 template<class T>
 const T* start_lifetime_as(const void* p) noexcept; // freestanding
 template<class T>
 volatile T* start_lifetime_as(volatile void* p) noexcept; // freestanding
 template<class T>
 const volatile T* start_lifetime_as(const volatile void* p) noexcept; // freestanding
 template<class T>
 T* start_lifetime_as_array(void* p, size_t n) noexcept; // freestanding
 template<class T>
 const T* start_lifetime_as_array(const void* p, size_t n) noexcept; // freestanding
 template<class T>
 volatile T* start_lifetime_as_array(volatile void* p,
 size_t n) noexcept; // freestanding
 template<class T>
 const volatile T* start_lifetime_as_array(const volatile void* p, // freestanding
 size_t n) noexcept;
 template<class T>
 T* trivially_relocate(T* first, T* last, T* result); // freestanding
 template<class T>
 constexpr T* relocate(T* first, T* last, T* result); // freestanding
 
 // allocator argument tag
 struct allocator_arg_t
 {
 explicit allocator_arg_t() = default;
 }; // freestanding
 inline constexpr allocator_arg_t allocator_arg{}; // freestanding
 
 // uses_allocator
 template<class T, class Alloc>
 struct uses_allocator; // freestanding
 
 // uses_allocator
 template<class T, class Alloc>
 constexpr bool uses_allocator_v = uses_allocator<T, Alloc>::value; // freestanding
 
 // uses-allocator construction
 template<class T, class Alloc, class... Args>
 constexpr auto uses_allocator_construction_args(const Alloc& alloc, // freestanding
 Args&&... args) noexcept;
 template<class T, class Alloc, class Tuple1, class Tuple2>
 constexpr auto uses_allocator_construction_args(const Alloc& alloc, // freestanding
 piecewise_construct_t,
 Tuple1&& x,
 Tuple2&& y) noexcept;
 template<class T, class Alloc>
 constexpr auto uses_allocator_construction_args(
 const Alloc& alloc) noexcept; // freestanding
 template<class T, class Alloc, class U, class V>
 constexpr auto uses_allocator_construction_args(const Alloc& alloc, // freestanding
 U&& u,
 V&& v) noexcept;
 template<class T, class Alloc, class U, class V>
 constexpr auto uses_allocator_construction_args(const Alloc& alloc, // freestanding
 pair<U, V>& pr) noexcept;
 template<class T, class Alloc, class U, class V>
 constexpr auto uses_allocator_construction_args(const Alloc& alloc, // freestanding
 const pair<U, V>& pr) noexcept;
 template<class T, class Alloc, class U, class V>
 constexpr auto uses_allocator_construction_args(const Alloc& alloc, // freestanding
 pair<U, V>&& pr) noexcept;
 template<class T, class Alloc, class U, class V>
 constexpr auto uses_allocator_construction_args(const Alloc& alloc, // freestanding
 const pair<U, V>&& pr) noexcept;
 template<class T, class Alloc, /*pair-like*/ P>
 constexpr auto uses_allocator_construction_args(const Alloc& alloc, // freestanding
 P&& p) noexcept;
 template<class T, class Alloc, class U>
 constexpr auto uses_allocator_construction_args(const Alloc& alloc, // freestanding
 U&& u) noexcept;
 template<class T, class Alloc, class... Args>
 constexpr T make_obj_using_allocator(const Alloc& alloc,
 Args&&... args); // freestanding
 template<class T, class Alloc, class... Args>
 constexpr T* uninitialized_construct_using_allocator(T* p, // freestanding
 const Alloc& alloc,
 Args&&... args);
 
 // allocator Traits
 template<class Alloc>
 struct allocator_traits; // freestanding
 
 template<class Pointer, class SizeType = size_t>
 struct allocation_result
 { // freestanding
 Pointer ptr;
 SizeType count;
 };
 
 // the default allocator
 template<class T>
 class allocator;
 template<class T, class U>
 constexpr bool operator==(const allocator<T>&, const allocator<U>&) noexcept;
 
 // addressof
 template<class T>
 constexpr T* addressof(T& r) noexcept; // freestanding
 template<class T>
 const T* addressof(const T&&) = delete; // freestanding
 
 // specialized algorithms
 // special memory concepts
 template<class I>
 concept no-throw-input-iterator = /* see description */; // exposition-only
 template<class I>
 concept no-throw-forward-iterator = /* see description */; // exposition-only
 template<class S, class I>
 concept no-throw-sentinel-for = /* see description */; // exposition-only
 template<class R>
 concept no-throw-input-range = /* see description */; // exposition-only
 template<class R>
 concept no-throw-forward-range = /* see description */; // exposition-only
 
 template<class NoThrowForwardIter>
 constexpr void uninitialized_default_construct(NoThrowForwardIter first, // freestanding
 NoThrowForwardIter last);
 template<class ExecutionPolicy, class NoThrowForwardIter>
 void uninitialized_default_construct(ExecutionPolicy&& exec, // freestanding-deleted,
 NoThrowForwardIter first,
 NoThrowForwardIter last);
 template<class NoThrowForwardIter, class Size>
 constexpr NoThrowForwardIter uninitialized_default_construct_n(NoThrowForwardIter first,
 Size n); // freestanding
 template<class ExecutionPolicy, class NoThrowForwardIter, class Size>
 NoThrowForwardIter uninitialized_default_construct_n(
 ExecutionPolicy&& exec, // freestanding-deleted,
 NoThrowForwardIter first,
 Size n);
 
 namespace ranges {
 template<no-throw-forward-iterator I, no-throw-sentinel-for<I> S>
 requires default_initializable<iter_value_t<I>>
 constexpr I uninitialized_default_construct(I first, S last); // freestanding
 template<no-throw-forward-range R>
 requires default_initializable<range_value_t<R>>
 constexpr borrowed_iterator_t<R> uninitialized_default_construct(
 R&& r); // freestanding
 
 template<no-throw-forward-iterator I>
 requires default_initializable<iter_value_t<I>>
 constexpr I uninitialized_default_construct_n(I first, // freestanding
 iter_difference_t<I> n);
 }
 
 template<class NoThrowForwardIter>
 constexpr void uninitialized_value_construct(NoThrowForwardIter first, // freestanding
 NoThrowForwardIter last);
 template<class ExecutionPolicy, class NoThrowForwardIter>
 void uninitialized_value_construct(ExecutionPolicy&& exec, // freestanding-deleted,
 NoThrowForwardIter first,
 NoThrowForwardIter last);
 template<class NoThrowForwardIter, class Size>
 constexpr NoThrowForwardIter uninitialized_value_construct_n(NoThrowForwardIter first,
 Size n); // freestanding
 template<class ExecutionPolicy, class NoThrowForwardIter, class Size>
 NoThrowForwardIter uninitialized_value_construct_n(
 ExecutionPolicy&& exec, // freestanding-deleted,
 NoThrowForwardIter first,
 Size n);
 
 namespace ranges {
 template<no-throw-forward-iterator I, no-throw-sentinel-for<I> S>
 requires default_initializable<iter_value_t<I>>
 constexpr I uninitialized_value_construct(I first, S last); // freestanding
 template<no-throw-forward-range R>
 requires default_initializable<range_value_t<R>>
 constexpr borrowed_iterator_t<R> uninitialized_value_construct(R&& r); // freestanding
 
 template<no-throw-forward-iterator I>
 requires default_initializable<iter_value_t<I>>
 constexpr I uninitialized_value_construct_n(I first, // freestanding
 iter_difference_t<I> n);
 }
 
 template<class InputIter, class NoThrowForwardIter>
 constexpr NoThrowForwardIter uninitialized_copy(InputIter first, // freestanding
 InputIter last,
 NoThrowForwardIter result);
 template<class ExecutionPolicy, class ForwardIter, class NoThrowForwardIter>
 NoThrowForwardIter uninitialized_copy(ExecutionPolicy&& exec, // freestanding-deleted,
 ForwardIter first,
 ForwardIter last,
 NoThrowForwardIter result);
 template<class InputIter, class Size, class NoThrowForwardIter>
 constexpr NoThrowForwardIter uninitialized_copy_n(InputIter first, // freestanding
 Size n,
 NoThrowForwardIter result);
 template<class ExecutionPolicy,
 class ForwardIter,
 class Size,
 class NoThrowForwardIter>
 NoThrowForwardIter uninitialized_copy_n(ExecutionPolicy&& exec, // freestanding-deleted,
 ForwardIter first,
 Size n,
 NoThrowForwardIter result);
 
 namespace ranges {
 template<class I, class O>
 using uninitialized_copy_result = in_out_result<I, O>; // freestanding
 template<input_iterator I,
 sentinel_for<I> S1,
 no-throw-forward-iterator O,
 no-throw-sentinel-for<O> S2>
 requires constructible_from<iter_value_t<O>, iter_reference_t<I>>
 constexpr uninitialized_copy_result<I, O>
 uninitialized_copy(I ifirst, S1 ilast, O ofirst, S2 olast); // freestanding
 template<input_range IR, no-throw-forward-range OR>
 requires constructible_from<range_value_t<OR>, range_reference_t<IR>>
 constexpr uninitialized_copy_result<borrowed_iterator_t<IR>, borrowed_iterator_t<OR>>
 uninitialized_copy(IR&& in_range, OR&& out_range); // freestanding
 
 template<class I, class O>
 using uninitialized_copy_n_result = in_out_result<I, O>; // freestanding
 template<input_iterator I,
 no-throw-forward-iterator O,
 no-throw-sentinel-for<O> S>
 requires constructible_from<iter_value_t<O>, iter_reference_t<I>>
 constexpr uninitialized_copy_n_result<I, O> uninitialized_copy_n(
 I ifirst,
 iter_difference_t<I> n, // freestanding
 O ofirst,
 S olast);
 }
 
 template<class InputIter, class NoThrowForwardIter>
 constexpr NoThrowForwardIter uninitialized_move(InputIter first, // freestanding
 InputIter last,
 NoThrowForwardIter result);
 template<class ExecutionPolicy, class ForwardIter, class NoThrowForwardIter>
 NoThrowForwardIter uninitialized_move(ExecutionPolicy&& exec, // freestanding-deleted,
 ForwardIter first,
 ForwardIter last,
 NoThrowForwardIter result);
 template<class InputIter, class Size, class NoThrowForwardIter>
 constexpr pair<InputIter, NoThrowForwardIter> uninitialized_move_n(
 InputIter first,
 Size n, // freestanding
 NoThrowForwardIter result);
 template<class ExecutionPolicy, class ForwardIter, class Size, class NoThrowForwardIter>
 pair<ForwardIter, NoThrowForwardIter> uninitialized_move_n(
 ExecutionPolicy&& exec, // freestanding-deleted,
 ForwardIter first,
 Size n,
 NoThrowForwardIter result);
 
 namespace ranges {
 template<class I, class O>
 using uninitialized_move_result = in_out_result<I, O>; // freestanding
 template<input_iterator I,
 sentinel_for<I> S1,
 no-throw-forward-iterator O,
 no-throw-sentinel-for<O> S2>
 requires constructible_from<iter_value_t<O>, iter_rvalue_reference_t<I>>
 constexpr uninitialized_move_result<I, O>
 uninitialized_move(I ifirst, S1 ilast, O ofirst, S2 olast); // freestanding
 template<input_range IR, no-throw-forward-range OR>
 requires constructible_from<range_value_t<OR>, range_rvalue_reference_t<IR>>
 constexpr uninitialized_move_result<borrowed_iterator_t<IR>, borrowed_iterator_t<OR>>
 uninitialized_move(IR&& in_range, OR&& out_range); // freestanding
 
 template<class I, class O>
 using uninitialized_move_n_result = in_out_result<I, O>; // freestanding
 template<input_iterator I,
 no-throw-forward-iterator O,
 no-throw-sentinel-for<O> S>
 requires constructible_from<iter_value_t<O>, iter_rvalue_reference_t<I>>
 constexpr uninitialized_move_n_result<I, O> uninitialized_move_n(
 I ifirst,
 iter_difference_t<I> n, // freestanding
 O ofirst,
 S olast);
 }
 
 template<class NoThrowForwardIter, class T>
 constexpr void uninitialized_fill(NoThrowForwardIter first, // freestanding
 NoThrowForwardIter last,
 const T& x);
 template<class ExecutionPolicy, class NoThrowForwardIter, class T>
 void uninitialized_fill(ExecutionPolicy&& exec, // freestanding-deleted,
 NoThrowForwardIter first,
 NoThrowForwardIter last,
 const T& x);
 template<class NoThrowForwardIter, class Size, class T>
 constexpr NoThrowForwardIter uninitialized_fill_n(NoThrowForwardIter first,
 Size n,
 const T& x); // freestanding
 template<class ExecutionPolicy, class NoThrowForwardIter, class Size, class T>
 NoThrowForwardIter uninitialized_fill_n(ExecutionPolicy&& exec, // freestanding-deleted,
 NoThrowForwardIter first,
 Size n,
 const T& x);
 
 namespace ranges {
 template<no-throw-forward-iterator I, no-throw-sentinel-for<I> S, class T>
 requires constructible_from<iter_value_t<I>, const T&>
 constexpr I uninitialized_fill(I first, S last, const T& x); // freestanding
 template<no-throw-forward-range R, class T>
 requires constructible_from<range_value_t<R>, const T&>
 constexpr borrowed_iterator_t<R> uninitialized_fill(R&& r,
 const T& x); // freestanding
 
 template<no-throw-forward-iterator I, class T>
 requires constructible_from<iter_value_t<I>, const T&>
 constexpr I uninitialized_fill_n(I first, // freestanding
 iter_difference_t<I> n,
 const T& x);
 }
 
 // construct_at
 template<class T, class... Args>
 constexpr T* construct_at(T* location, Args&&... args); // freestanding
 
 namespace ranges {
 template<class T, class... Args>
 constexpr T* construct_at(T* location, Args&&... args); // freestanding
 }
 
 // destroy
 template<class T>
 constexpr void destroy_at(T* location); // freestanding
 template<class NoThrowForwardIter>
 constexpr void destroy(NoThrowForwardIter first, // freestanding
 NoThrowForwardIter last);
 template<class ExecutionPolicy, class NoThrowForwardIter>
 void destroy(ExecutionPolicy&& exec, // freestanding-deleted,
 NoThrowForwardIter first,
 NoThrowForwardIter last);
 template<class NoThrowForwardIter, class Size>
 constexpr NoThrowForwardIter destroy_n(NoThrowForwardIter first, // freestanding
 Size n);
 template<class ExecutionPolicy, class NoThrowForwardIter, class Size>
 NoThrowForwardIter destroy_n(ExecutionPolicy&& exec, // freestanding-deleted,
 NoThrowForwardIter first,
 Size n);
 
 namespace ranges {
 template<destructible T>
 constexpr void destroy_at(T* location) noexcept; // freestanding
 
 template<no-throw-input-iterator I, no-throw-sentinel-for<I> S>
 requires destructible<iter_value_t<I>>
 constexpr I destroy(I first, S last) noexcept; // freestanding
 template<no-throw-input-range R>
 requires destructible<range_value_t<R>>
 constexpr borrowed_iterator_t<R> destroy(R&& r) noexcept; // freestanding
 
 template<no-throw-input-iterator I>
 requires destructible<iter_value_t<I>>
 constexpr I destroy_n(I first, iter_difference_t<I> n) noexcept; // freestanding
 }
 
 // class template unique_ptr
 template<class T>
 struct default_delete; // freestanding
 template<class T>
 struct default_delete<T[]>; // freestanding
 template<class T, class D = default_delete<T>>
 class unique_ptr; // freestanding
 template<class T, class D>
 class unique_ptr<T[], D>; // freestanding
 
 template<class T, class... Args>
 constexpr unique_ptr<T> make_unique(Args&&... args); // T is not array
 template<class T>
 constexpr unique_ptr<T> make_unique(size_t n); // T is U[]
 template<class T, class... Args>
 /* unspecified */ make_unique(Args&&...) = delete; // T is U[N]
 
 template<class T>
 constexpr unique_ptr<T> make_unique_for_overwrite(); // T is not array
 template<class T>
 constexpr unique_ptr<T> make_unique_for_overwrite(size_t n); // T is U[]
 template<class T, class... Args>
 /* unspecified */ make_unique_for_overwrite(Args&&...) = delete; // T is U[N]
 
 template<class T, class D>
 constexpr void swap(unique_ptr<T, D>& x, unique_ptr<T, D>& y) noexcept; // freestanding
 
 template<class T1, class D1, class T2, class D2>
 constexpr bool operator==(const unique_ptr<T1, D1>& x, // freestanding
 const unique_ptr<T2, D2>& y);
 template<class T1, class D1, class T2, class D2>
 bool operator<(const unique_ptr<T1, D1>& x,
 const unique_ptr<T2, D2>& y); // freestanding
 template<class T1, class D1, class T2, class D2>
 bool operator>(const unique_ptr<T1, D1>& x,
 const unique_ptr<T2, D2>& y); // freestanding
 template<class T1, class D1, class T2, class D2>
 bool operator<=(const unique_ptr<T1, D1>& x,
 const unique_ptr<T2, D2>& y); // freestanding
 template<class T1, class D1, class T2, class D2>
 bool operator>=(const unique_ptr<T1, D1>& x,
 const unique_ptr<T2, D2>& y); // freestanding
 template<class T1, class D1, class T2, class D2>
 requires three_way_comparable_with<typename unique_ptr<T1, D1>::pointer,
 typename unique_ptr<T2, D2>::pointer>
 compare_three_way_result_t<typename unique_ptr<T1, D1>::pointer,
 typename unique_ptr<T2, D2>::pointer>
 operator<=>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y); // freestanding
 
 template<class T, class D>
 constexpr bool operator==(const unique_ptr<T, D>& x,
 nullptr_t) noexcept; // freestanding
 template<class T, class D>
 constexpr bool operator<(const unique_ptr<T, D>& x, nullptr_t); // freestanding
 template<class T, class D>
 constexpr bool operator<(nullptr_t, const unique_ptr<T, D>& y); // freestanding
 template<class T, class D>
 constexpr bool operator>(const unique_ptr<T, D>& x, nullptr_t); // freestanding
 template<class T, class D>
 constexpr bool operator>(nullptr_t, const unique_ptr<T, D>& y); // freestanding
 template<class T, class D>
 constexpr bool operator<=(const unique_ptr<T, D>& x, nullptr_t); // freestanding
 template<class T, class D>
 constexpr bool operator<=(nullptr_t, const unique_ptr<T, D>& y); // freestanding
 template<class T, class D>
 constexpr bool operator>=(const unique_ptr<T, D>& x, nullptr_t); // freestanding
 template<class T, class D>
 constexpr bool operator>=(nullptr_t, const unique_ptr<T, D>& y); // freestanding
 template<class T, class D>
 requires three_way_comparable<typename unique_ptr<T, D>::pointer>
 constexpr compare_three_way_result_t<typename unique_ptr<T, D>::pointer> operator<=>(
 const unique_ptr<T, D>& x,
 nullptr_t); // freestanding
 
 template<class E, class T, class Y, class D>
 basic_ostream<E, T>& operator<<(basic_ostream<E, T>& os, const unique_ptr<Y, D>& p);
 
 // class bad_weak_ptr
 class bad_weak_ptr;
 
 // class template shared_ptr
 template<class T>
 class shared_ptr;
 
 // shared_ptr creation
 template<class T, class... Args>
 shared_ptr<T> make_shared(Args&&... args); // T is not array
 template<class T, class A, class... Args>
 shared_ptr<T> allocate_shared(const A& a, Args&&... args); // T is not array
 
 template<class T>
 shared_ptr<T> make_shared(size_t N); // T is U[]
 template<class T, class A>
 shared_ptr<T> allocate_shared(const A& a, size_t N); // T is U[]
 
 template<class T>
 shared_ptr<T> make_shared(); // T is U[N]
 template<class T, class A>
 shared_ptr<T> allocate_shared(const A& a); // T is U[N]
 
 template<class T>
 shared_ptr<T> make_shared(size_t N, const remove_extent_t<T>& u); // T is U[]
 template<class T, class A>
 shared_ptr<T> allocate_shared(const A& a,
 size_t N,
 const remove_extent_t<T>& u); // T is U[]
 
 template<class T>
 shared_ptr<T> make_shared(const remove_extent_t<T>& u); // T is U[N]
 template<class T, class A>
 shared_ptr<T> allocate_shared(const A& a, const remove_extent_t<T>& u); // T is U[N]
 
 template<class T>
 shared_ptr<T> make_shared_for_overwrite(); // T is not U[]
 template<class T, class A>
 shared_ptr<T> allocate_shared_for_overwrite(const A& a); // T is not U[]
 
 template<class T>
 shared_ptr<T> make_shared_for_overwrite(size_t N); // T is U[]
 template<class T, class A>
 shared_ptr<T> allocate_shared_for_overwrite(const A& a, size_t N); // T is U[]
 
 // shared_ptr comparisons
 template<class T, class U>
 bool operator==(const shared_ptr<T>& a, const shared_ptr<U>& b) noexcept;
 template<class T, class U>
 strong_ordering operator<=>(const shared_ptr<T>& a, const shared_ptr<U>& b) noexcept;
 
 template<class T>
 bool operator==(const shared_ptr<T>& x, nullptr_t) noexcept;
 template<class T>
 strong_ordering operator<=>(const shared_ptr<T>& x, nullptr_t) noexcept;
 
 // shared_ptr specialized algorithms
 template<class T>
 void swap(shared_ptr<T>& a, shared_ptr<T>& b) noexcept;
 
 // shared_ptr casts
 template<class T, class U>
 shared_ptr<T> static_pointer_cast(const shared_ptr<U>& r) noexcept;
 template<class T, class U>
 shared_ptr<T> static_pointer_cast(shared_ptr<U>&& r) noexcept;
 template<class T, class U>
 shared_ptr<T> dynamic_pointer_cast(const shared_ptr<U>& r) noexcept;
 template<class T, class U>
 shared_ptr<T> dynamic_pointer_cast(shared_ptr<U>&& r) noexcept;
 template<class T, class U>
 shared_ptr<T> const_pointer_cast(const shared_ptr<U>& r) noexcept;
 template<class T, class U>
 shared_ptr<T> const_pointer_cast(shared_ptr<U>&& r) noexcept;
 template<class T, class U>
 shared_ptr<T> reinterpret_pointer_cast(const shared_ptr<U>& r) noexcept;
 template<class T, class U>
 shared_ptr<T> reinterpret_pointer_cast(shared_ptr<U>&& r) noexcept;
 
 // shared_ptr get_deleter
 template<class D, class T>
 D* get_deleter(const shared_ptr<T>& p) noexcept;
 
 // shared_ptr I/O
 template<class E, class T, class Y>
 basic_ostream<E, T>& operator<<(basic_ostream<E, T>& os, const shared_ptr<Y>& p);
 
 // class template weak_ptr
 template<class T>
 class weak_ptr;
 
 // weak_ptr specialized algorithms
 template<class T>
 void swap(weak_ptr<T>& a, weak_ptr<T>& b) noexcept;
 
 // class template owner_less
 template<class T = void>
 struct owner_less;
 
 // struct owner_hash
 struct owner_hash;
 
 // struct owner_equal
 struct owner_equal;
 
 // class template enable_shared_from_this
 template<class T>
 class enable_shared_from_this;
 
 // hash support
 template<class T>
 struct hash; // freestanding
 template<class T, class D>
 struct hash<unique_ptr<T, D>>; // freestanding
 template<class T>
 struct hash<shared_ptr<T>>;
 
 // atomic smart pointers
 template<class T>
 struct atomic; // freestanding
 template<class T>
 struct atomic<shared_ptr<T>>;
 template<class T>
 struct atomic<weak_ptr<T>>;
 
 // class template out_ptr_t
 template<class Smart, class Pointer, class... Args>
 class out_ptr_t; // freestanding
 
 // function template out_ptr
 template<class Pointer = void, class Smart, class... Args>
 auto out_ptr(Smart& s, Args&&... args); // freestanding
 
 // class template inout_ptr_t
 template<class Smart, class Pointer, class... Args>
 class inout_ptr_t; // freestanding
 
 // function template inout_ptr
 template<class Pointer = void, class Smart, class... Args>
 auto inout_ptr(Smart& s, Args&&... args); // freestanding
 
 // class template indirect
 template<class T, class Allocator = allocator<T>>
 class indirect;
 
 // hash support
 template<class T, class Alloc>
 struct hash<indirect<T, Alloc>>;
 
 // class template polymorphic
 template<class T, class Allocator = allocator<T>>
 class polymorphic;
 
 namespace pmr {
 template<class T>
 using indirect = indirect<T, polymorphic_allocator<T>>;
 template<class T>
 using polymorphic = polymorphic<T, polymorphic_allocator<T>>;
 }
}

template<class I>
concept no-throw-input-iterator = // exposition only
 input_iterator<I> &&
 is_lvalue_reference_v<iter_reference_t<I>> &&
 same_as<remove_cvref_t<iter_reference_t<I>>, iter_value_t<I>>;
 
template<class S, class I>
concept no-throw-sentinel-for = sentinel_for<S, I>; // exposition only
 
template<class R>
concept no-throw-input-range = // exposition only
 ranges::range <R> &&
 no-throw-input-iterator <ranges::iterator_t <R>> &&
 no-throw-sentinel-for<ranges::sentinel_t <R>, ranges::iterator_t <R>>;
 
template<class I>
concept no-throw-forward-iterator = // exposition only
 no-throw-input-iterator <I> &&
 forward_iterator<I> &&
 no-throw-sentinel-for<I, I>;
 
template<class R>
concept no-throw-forward-range = // exposition only
 no-throw-input-range <R> &&
 no-throw-forward-iterator <ranges::iterator_t <R>>;

namespace std {
 template<class Ptr>
 struct pointer_traits
 {
 /* see description */;
 };
 
 template<class T>
 struct pointer_traits<T*>
 {
 using pointer = T*;
 using element_type = T;
 using difference_type = ptrdiff_t;
 
 template<class U>
 using rebind = U*;
 
 static constexpr pointer pointer_to(/* see description */ r) noexcept;
 };
}

namespace std {
 struct allocator_arg_t { explicit allocator_arg_t() = default; };
 inline constexpr allocator_arg_t allocator_arg{};
}

namespace std {
 template<class Alloc>
 struct allocator_traits
 {
 using allocator_type = Alloc;
 
 using value_type = typename Alloc::value_type;
 
 using pointer = /* see description */;
 using const_pointer = /* see description */;
 using void_pointer = /* see description */;
 using const_void_pointer = /* see description */;
 
 using difference_type = /* see description */;
 using size_type = /* see description */;
 
 using propagate_on_container_copy_assignment = /* see description */;
 using propagate_on_container_move_assignment = /* see description */;
 using propagate_on_container_swap = /* see description */;
 using is_always_equal = /* see description */;
 
 template<class T>
 using rebind_alloc = /* see description */;
 template<class T>
 using rebind_traits = allocator_traits<rebind_alloc<T>>;
 
 static constexpr pointer allocate(Alloc& a, size_type n);
 static constexpr pointer allocate(Alloc& a, size_type n, const_void_pointer hint);
 static constexpr allocation_result<pointer, size_type> allocate_at_least(Alloc& a,
 size_type n);
 
 static constexpr void deallocate(Alloc& a, pointer p, size_type n);
 
 template<class T, class... Args>
 static constexpr void construct(Alloc& a, T* p, Args&&... args);
 
 template<class T>
 static constexpr void destroy(Alloc& a, T* p);
 
 static constexpr size_type max_size(const Alloc& a) noexcept;
 
 static constexpr Alloc select_on_container_copy_construction(const Alloc& rhs);
 };
}

namespace std {
 template<class T>
 class allocator
 {
 public:
 using value_type = T;
 using size_type = size_t;
 using difference_type = ptrdiff_t;
 using propagate_on_container_move_assignment = true_type;
 
 constexpr allocator() noexcept;
 constexpr allocator(const allocator&) noexcept;
 template<class U>
 constexpr allocator(const allocator<U>&) noexcept;
 constexpr ~allocator();
 constexpr allocator& operator=(const allocator&) = default;
 
 constexpr T* allocate(size_t n);
 constexpr allocation_result<T*> allocate_at_least(size_t n);
 constexpr void deallocate(T* p, size_t n);
 };
}

namespace std {
 template<class T>
 struct default_delete
 {
 constexpr default_delete() noexcept = default;
 template<class U>
 constexpr default_delete(const default_delete<U>&) noexcept;
 constexpr void operator()(T*) const;
 };
 
 template<class T>
 struct default_delete<T[]>
 {
 constexpr default_delete() noexcept = default;
 template<class U>
 constexpr default_delete(const default_delete<U[]>&) noexcept;
 template<class U>
 constexpr void operator()(U* ptr) const;
 };
}

namespace std {
 template<class T, class D = default_delete<T>>
 class unique_ptr
 {
 public:
 using pointer = /* see description */;
 using element_type = T;
 using deleter_type = D;
 
 // constructors
 constexpr unique_ptr() noexcept;
 constexpr explicit unique_ptr(type_identity_t<pointer> p) noexcept;
 constexpr unique_ptr(type_identity_t<pointer> p, /* see description */ d1) noexcept;
 constexpr unique_ptr(type_identity_t<pointer> p, /* see description */ d2) noexcept;
 constexpr unique_ptr(unique_ptr&& u) noexcept;
 constexpr unique_ptr(nullptr_t) noexcept;
 template<class U, class E>
 constexpr unique_ptr(unique_ptr<U, E>&& u) noexcept;
 
 // destructor
 constexpr ~unique_ptr();
 
 // assignment
 constexpr unique_ptr& operator=(unique_ptr&& u) noexcept;
 template<class U, class E>
 constexpr unique_ptr& operator=(unique_ptr<U, E>&& u) noexcept;
 constexpr unique_ptr& operator=(nullptr_t) noexcept;
 
 // observers
 constexpr add_lvalue_reference_t<T> operator*() const noexcept(/* see description */);
 constexpr pointer operator->() const noexcept;
 constexpr pointer get() const noexcept;
 constexpr deleter_type& get_deleter() noexcept;
 constexpr const deleter_type& get_deleter() const noexcept;
 constexpr explicit operator bool() const noexcept;
 
 // modifiers
 constexpr pointer release() noexcept;
 constexpr void reset(pointer p = pointer()) noexcept;
 constexpr void swap(unique_ptr& u) noexcept;
 
 // disable copy from lvalue
 unique_ptr(const unique_ptr&) = delete;
 unique_ptr& operator=(const unique_ptr&) = delete;
 };
 
 template<class T, class D>
 class unique_ptr<T[], D>
 {
 public:
 using pointer = /* see description */;
 using element_type = T;
 using deleter_type = D;
 
 // constructors
 constexpr unique_ptr() noexcept;
 template<class U>
 constexpr explicit unique_ptr(U p) noexcept;
 template<class U>
 constexpr unique_ptr(U p, /* see description */ d) noexcept;
 template<class U>
 constexpr unique_ptr(U p, /* see description */ d) noexcept;
 constexpr unique_ptr(unique_ptr&& u) noexcept;
 template<class U, class E>
 constexpr unique_ptr(unique_ptr<U, E>&& u) noexcept;
 constexpr unique_ptr(nullptr_t) noexcept;
 
 // destructor
 constexpr ~unique_ptr();
 
 // assignment
 constexpr unique_ptr& operator=(unique_ptr&& u) noexcept;
 template<class U, class E>
 constexpr unique_ptr& operator=(unique_ptr<U, E>&& u) noexcept;
 constexpr unique_ptr& operator=(nullptr_t) noexcept;
 
 // observers
 constexpr T& operator[](size_t i) const;
 constexpr pointer get() const noexcept;
 constexpr deleter_type& get_deleter() noexcept;
 constexpr const deleter_type& get_deleter() const noexcept;
 constexpr explicit operator bool() const noexcept;
 
 // modifiers
 constexpr pointer release() noexcept;
 template<class U>
 constexpr void reset(U p) noexcept;
 constexpr void reset(nullptr_t = nullptr) noexcept;
 constexpr void swap(unique_ptr& u) noexcept;
 
 // disable copy from lvalue
 unique_ptr(const unique_ptr&) = delete;
 unique_ptr& operator=(const unique_ptr&) = delete;
 };
}

namespace std {
 class bad_weak_ptr : public exception
 {
 public:
 // for the specification of the special member functions
 const char* what() const noexcept override;
 };
}

namespace std {
 template<class T>
 class shared_ptr
 {
 public:
 using element_type = remove_extent_t<T>;
 using weak_type = weak_ptr<T>;
 
 // constructors
 constexpr shared_ptr() noexcept;
 constexpr shared_ptr(nullptr_t) noexcept
 : shared_ptr()
 {
 }
 template<class Y>
 explicit shared_ptr(Y* p);
 template<class Y, class D>
 shared_ptr(Y* p, D d);
 template<class Y, class D, class A>
 shared_ptr(Y* p, D d, A a);
 template<class D>
 shared_ptr(nullptr_t p, D d);
 template<class D, class A>
 shared_ptr(nullptr_t p, D d, A a);
 template<class Y>
 shared_ptr(const shared_ptr<Y>& r, element_type* p) noexcept;
 template<class Y>
 shared_ptr(shared_ptr<Y>&& r, element_type* p) noexcept;
 shared_ptr(const shared_ptr& r) noexcept;
 template<class Y>
 shared_ptr(const shared_ptr<Y>& r) noexcept;
 shared_ptr(shared_ptr&& r) noexcept;
 template<class Y>
 shared_ptr(shared_ptr<Y>&& r) noexcept;
 template<class Y>
 explicit shared_ptr(const weak_ptr<Y>& r);
 template<class Y, class D>
 shared_ptr(unique_ptr<Y, D>&& r);
 
 // destructor
 ~shared_ptr();
 
 // assignment
 shared_ptr& operator=(const shared_ptr& r) noexcept;
 template<class Y>
 shared_ptr& operator=(const shared_ptr<Y>& r) noexcept;
 shared_ptr& operator=(shared_ptr&& r) noexcept;
 template<class Y>
 shared_ptr& operator=(shared_ptr<Y>&& r) noexcept;
 template<class Y, class D>
 shared_ptr& operator=(unique_ptr<Y, D>&& r);
 
 // modifiers
 void swap(shared_ptr& r) noexcept;
 void reset() noexcept;
 template<class Y>
 void reset(Y* p);
 template<class Y, class D>
 void reset(Y* p, D d);
 template<class Y, class D, class A>
 void reset(Y* p, D d, A a);
 
 // observers
 element_type* get() const noexcept;
 T& operator*() const noexcept;
 T* operator->() const noexcept;
 element_type& operator[](ptrdiff_t i) const;
 long use_count() const noexcept;
 explicit operator bool() const noexcept;
 template<class U>
 bool owner_before(const shared_ptr<U>& b) const noexcept;
 template<class U>
 bool owner_before(const weak_ptr<U>& b) const noexcept;
 size_t owner_hash() const noexcept;
 template<class U>
 bool owner_equal(const shared_ptr<U>& b) const noexcept;
 template<class U>
 bool owner_equal(const weak_ptr<U>& b) const noexcept;
 };
 
 template<class T>
 shared_ptr(weak_ptr<T>) -> shared_ptr<T>;
 template<class T, class D>
 shared_ptr(unique_ptr<T, D>) -> shared_ptr<T>;
}

namespace std {
 template<class T>
 class weak_ptr
 {
 public:
 using element_type = remove_extent_t<T>;
 
 // constructors
 constexpr weak_ptr() noexcept;
 template<class Y>
 weak_ptr(const shared_ptr<Y>& r) noexcept;
 weak_ptr(const weak_ptr& r) noexcept;
 template<class Y>
 weak_ptr(const weak_ptr<Y>& r) noexcept;
 weak_ptr(weak_ptr&& r) noexcept;
 template<class Y>
 weak_ptr(weak_ptr<Y>&& r) noexcept;
 
 // destructor
 ~weak_ptr();
 
 // assignment
 weak_ptr& operator=(const weak_ptr& r) noexcept;
 template<class Y>
 weak_ptr& operator=(const weak_ptr<Y>& r) noexcept;
 template<class Y>
 weak_ptr& operator=(const shared_ptr<Y>& r) noexcept;
 weak_ptr& operator=(weak_ptr&& r) noexcept;
 template<class Y>
 weak_ptr& operator=(weak_ptr<Y>&& r) noexcept;
 
 // modifiers
 void swap(weak_ptr& r) noexcept;
 void reset() noexcept;
 
 // observers
 long use_count() const noexcept;
 bool expired() const noexcept;
 shared_ptr<T> lock() const noexcept;
 template<class U>
 bool owner_before(const shared_ptr<U>& b) const noexcept;
 template<class U>
 bool owner_before(const weak_ptr<U>& b) const noexcept;
 size_t owner_hash() const noexcept;
 template<class U>
 bool owner_equal(const shared_ptr<U>& b) const noexcept;
 template<class U>
 bool owner_equal(const weak_ptr<U>& b) const noexcept;
 };
 
 template<class T>
 weak_ptr(shared_ptr<T>) -> weak_ptr<T>;
}

namespace std {
 template<class T = void>
 struct owner_less;
 
 template<class T>
 struct owner_less<shared_ptr<T>>
 {
 bool operator()(const shared_ptr<T>&, const shared_ptr<T>&) const noexcept;
 bool operator()(const shared_ptr<T>&, const weak_ptr<T>&) const noexcept;
 bool operator()(const weak_ptr<T>&, const shared_ptr<T>&) const noexcept;
 };
 
 template<class T>
 struct owner_less<weak_ptr<T>>
 {
 bool operator()(const weak_ptr<T>&, const weak_ptr<T>&) const noexcept;
 bool operator()(const shared_ptr<T>&, const weak_ptr<T>&) const noexcept;
 bool operator()(const weak_ptr<T>&, const shared_ptr<T>&) const noexcept;
 };
 
 template<>
 struct owner_less<void>
 {
 template<class T, class U>
 bool operator()(const shared_ptr<T>&, const shared_ptr<U>&) const noexcept;
 template<class T, class U>
 bool operator()(const shared_ptr<T>&, const weak_ptr<U>&) const noexcept;
 template<class T, class U>
 bool operator()(const weak_ptr<T>&, const shared_ptr<U>&) const noexcept;
 template<class T, class U>
 bool operator()(const weak_ptr<T>&, const weak_ptr<U>&) const noexcept;
 
 using is_transparent = /* unspecified */;
 };
}

namespace std {
 struct owner_hash
 {
 template<class T>
 size_t operator()(const shared_ptr<T>&) const noexcept;
 
 template<class T>
 size_t operator()(const weak_ptr<T>&) const noexcept;
 
 using is_transparent = /* unspecified */;
 };
}

namespace std {
 struct owner_equal
 {
 template<class T, class U>
 bool operator()(const shared_ptr<T>&, const shared_ptr<U>&) const noexcept;
 template<class T, class U>
 bool operator()(const shared_ptr<T>&, const weak_ptr<U>&) const noexcept;
 template<class T, class U>
 bool operator()(const weak_ptr<T>&, const shared_ptr<U>&) const noexcept;
 template<class T, class U>
 bool operator()(const weak_ptr<T>&, const weak_ptr<U>&) const noexcept;
 
 using is_transparent = /* unspecified */;
 };
}

namespace std {
 template<class T>
 class enable_shared_from_this
 {
 protected:
 constexpr enable_shared_from_this() noexcept;
 enable_shared_from_this(const enable_shared_from_this&) noexcept;
 enable_shared_from_this& operator=(const enable_shared_from_this&) noexcept;
 ~enable_shared_from_this();
 
 public:
 shared_ptr<T> shared_from_this();
 shared_ptr<T const> shared_from_this() const;
 weak_ptr<T> weak_from_this() noexcept;
 weak_ptr<T const> weak_from_this() const noexcept;
 
 private:
 mutable weak_ptr<T> /*weak-this*/; // exposition-only
 };
}

namespace std {
 template<class T> struct atomic<shared_ptr<T>> {
 using value_type = shared_ptr<T>;
 static constexpr bool is_always_lock_free = /* implementation-defined */;
 
 bool is_lock_free() const noexcept;
 void store(shared_ptr<T> desired, memory_order order = memory_order::seq_cst) noexcept;
 shared_ptr<T> load(memory_order order = memory_order::seq_cst) const noexcept;
 operator shared_ptr<T>() const noexcept;
 
 shared_ptr<T> exchange(shared_ptr<T> desired,
 memory_order order = memory_order::seq_cst) noexcept;
 
 bool compare_exchange_weak(shared_ptr<T>& expected, shared_ptr<T> desired,
 memory_order success, memory_order failure) noexcept;
 bool compare_exchange_strong(shared_ptr<T>& expected, shared_ptr<T> desired,
 memory_order success, memory_order failure) noexcept;
 
 bool compare_exchange_weak(shared_ptr<T>& expected, shared_ptr<T> desired,
 memory_order order = memory_order::seq_cst) noexcept;
 bool compare_exchange_strong(shared_ptr<T>& expected, shared_ptr<T> desired,
 memory_order order = memory_order::seq_cst) noexcept;
 
 constexpr atomic() noexcept = default;
 atomic(shared_ptr<T> desired) noexcept;
 atomic(const atomic&) = delete;
 void operator=(const atomic&) = delete;
 void operator=(shared_ptr<T> desired) noexcept;
 
 private:
 shared_ptr<T> p; // exposition only
 };
}

namespace std {
 template<class T> struct atomic<weak_ptr<T>> {
 using value_type = weak_ptr<T>;
 static constexpr bool is_always_lock_free = /* implementation-defined */;
 
 bool is_lock_free() const noexcept;
 void store(weak_ptr<T> desired, memory_order order = memory_order::seq_cst) noexcept;
 weak_ptr<T> load(memory_order order = memory_order::seq_cst) const noexcept;
 operator weak_ptr<T>() const noexcept;
 
 weak_ptr<T> exchange(weak_ptr<T> desired,
 memory_order order = memory_order::seq_cst) noexcept;
 
 bool compare_exchange_weak(weak_ptr<T>& expected, weak_ptr<T> desired,
 memory_order success, memory_order failure) noexcept;
 bool compare_exchange_strong(weak_ptr<T>& expected, weak_ptr<T> desired,
 memory_order success, memory_order failure) noexcept;
 
 bool compare_exchange_weak(weak_ptr<T>& expected, weak_ptr<T> desired,
 memory_order order = memory_order::seq_cst) noexcept;
 bool compare_exchange_strong(weak_ptr<T>& expected, weak_ptr<T> desired,
 memory_order order = memory_order::seq_cst) noexcept;
 
 constexpr atomic() noexcept = default;
 atomic(weak_ptr<T> desired) noexcept;
 atomic(const atomic&) = delete;
 void operator=(const atomic&) = delete;
 void operator=(weak_ptr<T> desired) noexcept;
 
 private:
 weak_ptr<T> p; // exposition only
 };
}

namespace std {
 template<class Smart, class Pointer, class... Args>
 class out_ptr_t
 {
 public:
 explicit out_ptr_t(Smart&, Args...);
 out_ptr_t(const out_ptr_t&) = delete;
 
 ~out_ptr_t();
 
 operator Pointer*() const noexcept;
 operator void**() const noexcept;
 
 private:
 Smart& s; // exposition-only
 tuple<Args...> a; // exposition-only
 Pointer p; // exposition-only
 };
}

namespace std {
 template<class Smart, class Pointer, class... Args>
 class inout_ptr_t
 {
 public:
 explicit inout_ptr_t(Smart&, Args...);
 inout_ptr_t(const inout_ptr_t&) = delete;
 
 ~inout_ptr_t();
 
 operator Pointer*() const noexcept;
 operator void**() const noexcept;
 
 private:
 Smart& s; // exposition-only
 tuple<Args...> a; // exposition-only
 Pointer p; // exposition-only
 };
}

namespace std {
 template<class T, class Allocator = allocator<T>>
 class indirect
 {
 public:
 using value_type = T;
 using allocator_type = Allocator;
 using pointer = typename allocator_traits<Allocator>::pointer;
 using const_pointer = typename allocator_traits<Allocator>::const_pointer;
 
 // constructors
 constexpr explicit indirect();
 constexpr explicit indirect(allocator_arg_t, const Allocator& a);
 constexpr indirect(const indirect& other);
 constexpr indirect(allocator_arg_t, const Allocator& a, const indirect& other);
 constexpr indirect(indirect&& other) noexcept;
 constexpr indirect(allocator_arg_t,
 const Allocator& a,
 indirect&& other) noexcept(/* see description */);
 template<class U = T>
 constexpr explicit indirect(U&& u);
 template<class U = T>
 constexpr explicit indirect(allocator_arg_t, const Allocator& a, U&& u);
 template<class... Us>
 constexpr explicit indirect(in_place_t, Us&&... us);
 template<class... Us>
 constexpr explicit indirect(allocator_arg_t,
 const Allocator& a,
 in_place_t,
 Us&&... us);
 template<class I, class... Us>
 constexpr explicit indirect(in_place_t, initializer_list<I> ilist, Us&&... us);
 template<class I, class... Us>
 constexpr explicit indirect(allocator_arg_t,
 const Allocator& a,
 in_place_t,
 initializer_list<I> ilist,
 Us&&... us);
 
 // destructor
 constexpr ~indirect();
 
 // assignment
 constexpr indirect& operator=(const indirect& other);
 constexpr indirect& operator=(indirect&& other) noexcept(/* see description */);
 template<class U = T>
 constexpr indirect& operator=(U&& u);
 
 // observers
 constexpr const T& operator*() const& noexcept;
 constexpr T& operator*() & noexcept;
 constexpr const T&& operator*() const&& noexcept;
 constexpr T&& operator*() && noexcept;
 constexpr const_pointer operator->() const noexcept;
 constexpr pointer operator->() noexcept;
 constexpr bool valueless_after_move() const noexcept;
 constexpr allocator_type get_allocator() const noexcept;
 
 // swap
 constexpr void swap(indirect& other) noexcept(/* see description */);
 friend constexpr void swap(indirect& lhs,
 indirect& rhs) noexcept(/* see description */);
 
 // relational operators
 template<class U, class AA>
 friend constexpr bool operator==(
 const indirect& lhs,
 const indirect<U, AA>& rhs) noexcept(/* see description */);
 template<class U, class AA>
 friend constexpr auto operator<=>(const indirect& lhs, const indirect<U, AA>& rhs)
 -> /*synth-three-way-result*/<T, U>;
 
 // comparison with T
 template<class U>
 friend constexpr bool operator==(const indirect& lhs,
 const U& rhs) noexcept(/* see description */);
 template<class U>
 friend constexpr auto operator<=>(const indirect& lhs, const U& rhs)
 -> /*synth-three-way-result*/<T, U>;
 
 private:
 pointer /*p*/; // exposition-only
 Allocator /*alloc*/ = Allocator(); // exposition-only
 };
 template<class Value>
 indirect(Value) -> indirect<Value>;
 template<class Allocator, class Value>
 indirect(allocator_arg_t, Allocator, Value)
 -> indirect<Value,
 typename allocator_traits<Allocator>::template rebind_alloc<Value>>;
}

namespace std {
 template<class T, class Allocator = allocator<T>>
 class polymorphic
 {
 public:
 using value_type = T;
 using allocator_type = Allocator;
 using pointer = typename allocator_traits<Allocator>::pointer;
 using const_pointer = typename allocator_traits<Allocator>::const_pointer;
 
 // constructors
 constexpr explicit polymorphic();
 constexpr explicit polymorphic(allocator_arg_t, const Allocator& a);
 constexpr polymorphic(const polymorphic& other);
 constexpr polymorphic(allocator_arg_t, const Allocator& a, const polymorphic& other);
 constexpr polymorphic(polymorphic&& other) noexcept;
 constexpr polymorphic(allocator_arg_t,
 const Allocator& a,
 polymorphic&& other) noexcept(/* see description */);
 template<class U = T>
 constexpr explicit polymorphic(U&& u);
 template<class U = T>
 constexpr explicit polymorphic(allocator_arg_t, const Allocator& a, U&& u);
 template<class U, class... Ts>
 constexpr explicit polymorphic(in_place_type_t<U>, Ts&&... ts);
 template<class U, class... Ts>
 constexpr explicit polymorphic(allocator_arg_t,
 const Allocator& a,
 in_place_type_t<U>,
 Ts&&... ts);
 template<class U, class I, class... Us>
 constexpr explicit polymorphic(in_place_type_t<U>,
 initializer_list<I> ilist,
 Us&&... us);
 template<class U, class I, class... Us>
 constexpr explicit polymorphic(allocator_arg_t,
 const Allocator& a,
 in_place_type_t<U>,
 initializer_list<I> ilist,
 Us&&... us);
 
 // destructor
 constexpr ~polymorphic();
 
 // assignment
 constexpr polymorphic& operator=(const polymorphic& other);
 constexpr polymorphic& operator=(polymorphic&& other) noexcept(/* see description */);
 
 // observers
 constexpr const T& operator*() const noexcept;
 constexpr T& operator*() noexcept;
 constexpr const_pointer operator->() const noexcept;
 constexpr pointer operator->() noexcept;
 constexpr bool valueless_after_move() const noexcept;
 constexpr allocator_type get_allocator() const noexcept;
 
 // swap
 constexpr void swap(polymorphic& other) noexcept(/* see description */);
 friend constexpr void swap(polymorphic& lhs,
 polymorphic& rhs) noexcept(/* see description */);
 
 private:
 Allocator /*alloc*/ = Allocator(); // exposition-only
 };
}