Problem:
Score : 200 points

Problem Statement

Takahashi loves palindromes. Non-palindromic strings are unacceptable to him. Each time he hugs a string, he can change one of its characters to any character of his choice.

Given is a string S. Find the minimum number of hugs needed to make S palindromic.

Constraints

S is a string consisting of lowercase English letters.

The length of S is between 1 and 100 (inclusive).

Input

Input is given from Standard Input in the following format:

S

Output

Print the minimum number of hugs needed to make S palindromic.

Sample Input 1

redcoder

Sample Output 1

1

For example, we can change the fourth character to o and get a palindrome redooder.

Sample Input 2

vvvvvv

Sample Output 2

0

We might need no hugs at all.

Sample Input 3

abcdabc

Sample Output 3

2

Solution in Python (3.4.3) (judge verdict: Accepted)

def main():
  S = input()
  half = int(len(S) / 2) if len(S) % 2 == 0 else int((len(S) - 1) / 2)
  first = []
  latter = []
  count = 0

  for i in range(half):
    first.append(S[i])
    latter.append(S[-i-1])

  for i in range(half):
    count += 0 if first[i] == latter[i] else 1

  print(count)
  

if __name__ == '__main__':
  main()