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# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
class Program
{

    static void Main(string[] args)
    {

        // input with space delimiter
        string input = Console.ReadLine();
        var characters = input.ToCharArray();
        int n = input.Length;
        int cnt = 0;
        for ( int i = 0; i <= n/2-1; i++)
        {
            if (characters[i] != characters[n - i - 1])
                cnt++;
        }

        Console.WriteLine(cnt);

    }
}