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)

#%%
import sys
def input():
    return sys.stdin.readline().rstrip()

def main():
    S=input()

    o=list(S)
    r=list(reversed(o))
    cnt=0
    for i in range(len(S)//2):
        if o[i]!=r[i]:
            cnt += 1
    print(cnt)


# %%
if __name__ == '__main__':
    main()

# %%
# from atcoder_test import doTest
# doTest("abc147","b",main)