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)

//回文
using System;

namespace tst
{
    
    class Program
    {
        public static void Main()
        {
            string text = Console.ReadLine();
            //回文が奇数か偶数かで分岐はしなくても平気
            int len = text.Length;
            //文字が一致してないときカウント
            int cnt = 0;
            for(int i=0; i <= (len / 2)-1; i++)
            {
                if (text.Substring(i,1) != text.Substring(len-1-i,1))
                {//文字が一致しなかったら
                    cnt++;
                }
            }
            Console.WriteLine(cnt);
            
        }

    }
}