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		num;
  	int		len;
  	int		i;
  	int		count;
  
  	num = scanf("%s", s);
  	if (num != 1)
      	return (0);
  
  	len = strlen(s);
  
  	count = 0;
  	for (i=0; i<len/2 ; i++)
    {
      	if (s[i] != s[len - i - 1])
          	count++;
    }
  
  	printf("%d", count);
  
  	return (0);
}