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: Wrong Answer)

#include <stdio.h>
#include <string.h>
void rev(char *s){
    int l=strlen(s),i;
    for(i=0;i<l/2;i++){
        char t=s[i];
        s[i]=s[l-1-i];
        s[l-1-i]=t;
    }
}

int main(){
    int i,c,l;
  	int counter = 0;
    char s[512];
  	char copy[512];
    scanf("%s",s);
    l=strlen(s);
  	strcpy(copy,s);
    rev(s);
    for(i=0;i<l;i++){
    	if(s[i] != copy[i]) {
            counter++;
        }
    }
  	counter--;
  	if(counter < 0) counter =0;
    printf("%d\n",counter);
    return 0;
}