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 static System.Console;
using static System.Math;

namespace B_ABC147
{
    class MainClass
    {

        //static int[] s;

        public static void Main(string[] args)
        {
            string s1 = ReadLine();
            string s2 = new string(s1.Reverse().ToArray()); // olleh
            int cnt = 0;
            for(int i= 0;i<s1.Length/2;i++){
                if(s1[i]!=s2[i]){
                    cnt++;

                }
            }
            WriteLine(cnt);
        }
    }
}