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(void)
{
	char s[101];
	int charCount = 0, hugCount = 0;
	int i = 0;

	scanf("%s", s);

	/* 文字列の文字数を数える */
	charCount = strlen(s);

	/* 対称の位置にある文字同士を比較するので、ループは文字数の半分の回数 */
	for (i = 0; i < charCount / 2; i++)
	{
		/* 対称の位置にある文字が異なるとき、文字を変える必要がある */
		if (s[i] != s[charCount - 1 - i])
		{
			hugCount++;
		}
	}

	printf("%d\n", hugCount);

	return 0;
}