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)

S = input()

half_length = int(len(S) / 2)
cnt = 0
front = []
back = []

if len(S) % 2 == 0:
    front = list(S[ 0 : half_length ])
    back = list((S[ half_length : len(S)]))
else:
    front = list((S[ 0 : int(len(S) / 2) ]))
    back = list((S[ int(len(S) / 2) + 1 : len(S)]))


back.reverse()

for i in range(len(front)):
    if front[i] != back[i]:
        cnt += 1

print(cnt)