import math


def bisection(function, a, b): # finds where the function becomes 0 in [a,b] using bolzano

 start = a
 end = b
 if function(a) == 0: # one of the a or b is a root for the function
 return a
 elif function(b) == 0:
 return b
 elif function(a) * function(b) > 0: # if none of these are root and they are both positive or negative,
 # then his algorithm can't find the root
 print("couldn't find root in [a,b]")
 return
 else:
 mid = (start + end) / 2
 while abs(start - mid) > 10**-7: # until we achieve precise equals to 10^-7
 if function(mid) == 0:
 return mid
 elif function(mid) * function(start) < 0:
 end = mid
 else:
 start = mid
 mid = (start + end) / 2
 return mid


def f(x):
 return math.pow(x, 3) - 2*x - 5

if __name__ == "__main__":
 print(bisection(f, 1, 1000))