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 <iostream>
#include <vector>
#include <unordered_map>
#include <map>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <deque>
#include <cmath>
#include <stack>
#include <queue>
#include <string>
#include <locale>
#include <iomanip>
#include <math.h>

#define nl '\n'

using namespace std;

string s;
int x;

int main(){

    cin >> s;

    vector<char> v;
    vector<char> v2;

    for(int i = 0; i < s.length(); i++){
        v.push_back(s[i]);
        v2.push_back(s[i]);
    }

    reverse(v.begin(), v.end());

    for(int i = 0; i < v.size(); i++){
        if(v[i] != v2[i]){
            x++;
        }
    }

    cout << x/2;




}

//g++ -std=c++14 comp.cpp -o b; ./b.exe