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;

static class StringExtention {
    public static string Reversed(this string s) {
        return string.Join("", s.Reverse());
    }
}

class Program
{
	static void Main(string[] args)
	{
		// 入力
        string a = Console.ReadLine();
		string b = a.Reversed();
        
        var count = 0;
        for (int i = 0; i < a.Length; i++)
        {
            if (a[i] != b[i])
            {
                count++;
            }
        }

        Console.WriteLine(count/2);


	}
}