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;
using System.Threading.Tasks;

namespace abc147_b
{
    class Program
    {
        static void Main(string[] args)
        {
            string input = Console.ReadLine();
            int value = input.Length;
            int hug = 0;  //hug回数の初期値
            string[] a = new string[value];
            for (int i = 0; i < value; ++i)
            {
                a[i] = input.Substring(i, 1);
            }
            for(int i = 0; i < (value / 2); ++i)
            {
                if (a[i] != a[value - (i+1)])
                {
                    hug++;
                }
            }
            Console.WriteLine(hug);
        }
    }
}