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 (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
#include <string.h>

int main() {
	char s[101], w[101], q[101];
	int a, as, ans = 0, i, o = 0, u;
	
	scanf("%s", s);
	
	a = strlen(s);
	
	as = a / 2;
	
	for(i = 0;i < as;i++) {
		o++;
		q[i] = s[i];
		w[i] = s[a-o];
	}
	
	for(u = 0;u < as;u++) {	
		if(s[u] != w[u])	ans = ans + 1;
	}
	
	printf("%d", ans);
	
	return 0;
	
}