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: Runtime Error)

#include <stdio.h>
void main()
{
	int n, i, m, k = 0;
	char s[100];
	
	for(n = 0; n < 100; n++){
		s[n] = '0';
	}
	
	scanf("%s", &s);
	
	n = 0;
	while(s[n] != '0'){
		i = n;
		n++;
	}
	
	i = i - 1;
	//printf("%d\n", i);
	
	m = i / 2;
	
	for(n = 0; n <= m; n++){
		if(s[n] != s[i - n]){
			k++;
		}
	}
	
	printf("%d", k);
}