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 C++ (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;

int main(){
    string s;
    cin >> s;

    int cnt = 0;
    // 奇数
    if(s.length() % 2){
        for(int i = 0; i < (int)s.length() * .5; i++){
            if(s[i] != s[s.length() - 1 - i]) cnt++;
        }
    }
    else{// 偶数
        for(int i = 0; i < (int)s.length() * .5; i++){
            if(s[i] != s[s.length() - 1 - i]) cnt++;
        }
    }

    cout << cnt << endl;
    
    return 0;
}