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>

int main(void){

  char s[101];
  int end;
  for (int i = 0; i < 101; i++) {
    scanf("%c", &s[i]);
    if (s[i] < 'a' || s[i] > 'z') {
      end = i;
      break;
    }
  }

  int hugs = 0;
  for (int i = 0; i < end/2; i++) {
    if (s[i] != s[end-1-i]) {
      hugs++;
    }
  }

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

  return 0;
}