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 9.2.1) (judge verdict: Accepted)

#include<stdio.h>
#include<string.h>
int main(void)
{
    int n,p;
    char s[100];
    scanf("%s",s);
    n = strlen(s) - 1;
    int i,count = 0;
    if (n % 2 == 0)
    {
        for(i = 0 ; i < (n / 2)  ; i++)
        {
            if(s[i] != s[n - i])
            {
                count++;
            }
        }
    }
    else
    {
        for(i = 0 ; i <= n / 2 ; i++)
        {
            if(s[i] != s[n - i])
            {
                count++;
            }
        }
    }
    printf("%d\n",count);
    return 0;
}