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 <cstdio>
#include <iostream>
#include <string>
#include <cmath>

using namespace std;

int main(){
	int leng;
	string S;
	int ans = 0;

	cin >> S;
	leng = S.length();
//	cout << leng;

	for(int i=0;i<leng/2;i++){
//		cout << S[i] << " " << S[leng-i-1] << endl;
//		printf("%d %d",S[i],S[leng-i]);
		if(S[i]!=S[leng-i-1]){
			ans++;
		}
	}
	printf("%d",ans);



	return 0;
}