def letters(s):
 return ''.join(a for a in s if a.isalpha())


def reverse(s):
 if s=="":
 return s
 else:
 return reverse(s[1:])+s[0]

str=input("请输入一个字符串:")
print("剔除非英文字母后:")
print(letters(str))
m=letters(str)
print("字符串反转输出:")
print(reverse(m))