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 Perl (v5.18.2) (judge verdict: Wrong Answer)

use strict;
use warnings;

my $str = <STDIN>;
chomp $str;

my @str_array = split(q{}, $str);
my $len       = @str_array;

my $count = 0;
my $i     = 0;
for my $s ( @str_array[0..int($len/2)-1] ) {
    $count += 1 if $s != $str_array[$len-1-$i];
    $i++;
}
print $count;