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: Runtime Error)

#include <iostream>
#include <string>
#include <cstring>
#include <fstream>
#include <cmath>
#include <iomanip>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <map>
#include <deque>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <list>
#include <unordered_map>
#include <bitset>
#include <sstream>

typedef  long long ll;
#define mop 1000000007
using namespace std;

int main() {
   

    string s;
    cin >> s;
    ll lenS = s.length();
    ll ans = 0;
//    if(lenS%2 == 0){
        ll tmp = 0;
        while(true) {
            if (s[tmp] != s[s.length() - 1 - tmp]) {
                ans++;
            }
            tmp++;
            if (tmp == lenS / 2) break;
        }
        cout << ans << endl;
//
//    }else{
//        ll tmp = 0;
//        while(true) {
//            if (s[tmp] != s[s.length() - 1 - tmp]) {
//                ans++;
//            }
//            tmp++;
//            if(tmp == lenS/2) break;
//        }
//    }
}