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>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#define pai 3.1415926535

int main(void) {
	char S[101];
	scanf("%s", S);
	int a = strlen(S);
	int count = 0;

	if(a%2==0){
		for (int i = 0; i < strlen(S)/2; i++) {
			if (S[i] != S[a - 1]) {
				count++;
			}

			a--;
		}
	}
	else {
		for (int i = 0; i <(strlen(S)-1) / 2; i++) {
			if (S[i] != S[a - 1]) {
				count++;
			}
			a--;
		}
	}
	printf("%d", count);


	return 0;
}