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<math.h>

int main(void){
	int i,j,k,z;
	int n=0;
	int count = 0;

	char s[100];
	scanf("%s", &s);
	while (s[n]!='\0'){
		n++;
	}
	if (n % 2 == 0) {
		j = n / 2;
		z = j - 1;
	}
	else {
		j = (n / 2) + 1;
		z = j - 2;
	}
	for (i = 0; i <= z; i++) {
		if (s[i] != s[n-1-i]) {
			count++;
		}
	}
	//printf("n=%d\nj=%d\nz=%d\n", n, j, z);
	printf("%d\n", count);
	return 0;
}