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 (Clang 3.8.0) (judge verdict: Accepted)

#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<set>
#include<string>
#include<stdio.h>

using namespace std;

#define rep(i, n) for(int i = 0; i < n; i++)
#define repn(i, n) for(int i = 1; i <= n; i++)
#define all(x) (x).begin(), (x).end()
#define lint long long

int main(){
    string s; cin>>s;
    int n = s.size();
    int i, j;
    i = 0; j = n-1;
    int ans = 0;
    while(j - i > 0){
        if(s[i] != s[j]) ans++;
        i++; j--;
    }
    cout<<ans<<endl;
}