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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php
  fscanf(STDIN, "%s", $s);
  $len = (int)strlen($s);
  $count = 0;
  $array = str_split($s);
  for($i = 0; $i < $len; $i ++){
  	if($array[$i] !== $array[$len - $i -1]){
    	$array[$i] = $array[$len - $i -1];
        $count += 1 ;
    }
  }
  echo $count;
  ?>