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>
using namespace std;

string FILENAME = "template";
#define io ifstream fin(FILENAME + ".in"); ofstream fout(FILENAME + ".out")
#define fwrite(X) fout << X;
#define fwriteln(X) fout << X << endl;

#define forl(V, N) for(int V = 0; V < N; V++)
#define forll(V, S, E) for(int V = S; V < E; V++)
#define fore(V, N) for(auto &V:N)
#define print(X) cout << X
#define printsp(X) cout << X << " "
#define println(X) cout << X << endl
#define rem(X) X.top(); X.pop()
#define graph unordered_map<int, vector<int>>
#define vi vector<int>
#define pb push_back
#define ll long long

int main() {
    string S;
    cin >> S;
    int sol = 0;
    forl(i, S.size()/2) {
        if(S[i] != S[S.size()-i-1]) sol++;
    }
    println(sol);
}