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)

str = input()
l = len(str)
p = l-1
index = 0
cnt=0
if l==1:
    print(0)
    exit()
if l==2:
    if str[0]==str[1]:
        print(0)
        exit()
    else:
        print(1)
        exit()
while index < p:

    if str[index] == str[p]:
        index = index + 1
        p = p-1
        if index == p or index + 1 == p:
            if str[index] == str[p]:
                print(cnt)
                exit()
            else:
                cnt+=1
                print(cnt)
                exit()
    else:
        cnt+=1
        index = index + 1
        p = p-1
        if index == p or index + 1 == p:
            if str[index] == str[p]:
                print(cnt)
                exit()
            else:
                cnt+=1
                print(cnt)
                exit()