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.Linq;
using System.Collections.Generic;
using System.IO;


class Program
{
   
    public static long Read()
    {
        return long.Parse(Console.ReadLine());
    }

    public static long[] Reads()
    {
        return Console.ReadLine().Split().Select(long.Parse).ToArray();
    }


    public static void Main()
    {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        Console.SetOut(sw);


        var s = Console.ReadLine();
        var c = s.ToCharArray();
        var count = 0;
        for(int i = 0; i < s.Length / 2 + 1; i++)
        {
            if (c[i] != c[s.Length - 1 - i])
            {
                count++;
                c[i] = c[s.Length - 1 - i];
            }
        }

        Console.WriteLine(count);


        Console.Out.Flush();

    }
}