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 PyPy3 (2.4.0) (judge verdict: Wrong Answer)

s = input()
a = []
b = []
cnt = 0
if len(s)%2 == 0:
    a = list(s[:int(len(s)/2)])
    b = list(s[int(len(s)/2):])
else:
    a = list(s[:int((len(s)-1)/2)])
    b = list(s[int((len(s)+1)/2):])
for i in range(len(a)):
    b.reverse()
    if a[i] != b[i]:
        cnt += 1
print(cnt)