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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
#define rep(i, a, b) for (long long i = (a); i < (b); i++)
#define rep2(r, aa, bb) for (long long r = (aa); r >= (bb); r--)
using namespace std;

int main()
{
    string s;
    cin >> s;
    int a = 0, b = 0, it = s.size()-1;
    rep(i,0,s.size()/2){
        if(s[i]!=s[it]){
            a++;
        }
        it--;
    }
    cout << a << endl;
}