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 <stdlib.h>
#include <math.h>
#include <string.h>
#define yes "Yes\n"
#define no "No\n"
//int m,n;
//int i,j,k,l;
//int a,b,c,d,e,f,g;
//int sum,total;
//long long int ;
//float ;
//double ;
//char a[101],b[101],s[101],t[101],u[101];
char s[101];
int i,k;
int main(void){
    scanf("%s",s);
    for (i = 0; i < strlen(s) / 2; i++)
    {
        if (s[i] != s[strlen(s)-i-1])
        {
            k++;
        }
    }
    printf("%d\n",k);
    return 0;
}