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 9.2.1) (judge verdict: Accepted)

#include <cstdio>
#include <bits/stdc++.h>
#include <algorithm>
#include <iostream>
#include <string>
#include <cmath>
#include <functional>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#define rep(i,n) for (int i=0;i<n;i++)
using ll = long long;
using namespace std;

void solve(){

}
int main (){
    ios::sync_with_stdio(0);
    cin.tie(0);
    string s;
    cin >> s;
    string g = s;
    reverse(s.begin(),s.end());
    int cnt=0;
    rep(i,s.size()){
        if(s[i]!=g[i]){
            cnt++;
        }
    }
    if(cnt%2==0){
        cout << cnt/2;
    }
    else{
        cout << cnt/2+1;
    }
    return 0;
}