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>
#define F first
#define S second
#define pb push_back
#define mp make_pair
#define full(a) a.begin(),a.end()
#define rfull(a) a.rbegin(),a.rend()

using namespace std;
const double pi=acos(-1.0);
const double pii=2*pi;
const double eps=1e-6;
const long long MOD=1e9+7;

void solve(){
	string s;
	cin>>s;
	int n = s.size();
	int ctr=0;
	for(int i=0;i<n;i++){
		if(i <= n-1-i && s[i]!=s[n-1-i])
			ctr++;
	}
	cout <<ctr<<"\n";
}

int main(){
	std::ios::sync_with_stdio(false);
	std::cin.tie(NULL);
	std::cout.tie(NULL);
	
	solve();
	return 0;
}