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;
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class Program
{
    static void Main()
    {
        string line = Console.ReadLine().Trim();

        int result = 0;
        var orikaesi = Math.Ceiling((decimal)line.Length / 2);

        for (int i = 1; i <= orikaesi; i++)
        {
            if (line.Substring(i - 1, 1) == line.Substring(line.Length - i, 1)) continue;

            result++;
        }

        Console.WriteLine(result.ToString());
    }
}