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 = list(input())
N = len(S)
# print(S)

if N % 2 == 0:
    div = int(N / 2)
else:
    div = int(N // 2)

# print(type(div),div)
S_pic = S[:div]
S_rev = list(reversed(S[div:]))

# print(S_pic)
# print(S_rev)

count = 0
for i in range(div):
    if S_pic[i] != S_rev[i]:
        count += 1

print(count)