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 PHP (7.4.4) (judge verdict: Accepted)

<?php
  fscanf(STDIN,"%s",$s);
 $j = strlen($s)-1;
 $c = 0;
 for($i=0;$i<(int)(strlen($s)/2);$i++){
   if($s[$j] != $s[$i]){
     $c++;
   }
   $j--;
 }
 echo $c;