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: Accepted)

import sys
input = sys.stdin.readline

S = input()
l = len(S)
count = 0
if len(S)%2 == 1:
    #print("here")
    for i in range(int(len(S)/2)):
        #print(S[i], S[l-i-2])
        if S[i] != S[l-i-2]:
            count += 1
else:
    for i in range(int((len(S)-1)/2)):
        #print(S[i], S[l-i-2])
        if S[i] != S[l-i-2]:
            count += 1

print(count)