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 Palindrome_philia
{
    class Program
    {
        static void Main(string[] args)
        {
            String S = Console.ReadLine();
            char[] c = S.ToCharArray();
            var l = S.Length;

            int cnt = 0;

            for (int i = 1; i <= l / 2; i++)
            {
                //if (even)
                //{
                    if (c[i-1] != c[l-i])
                    {
                        c[l - i] = c[i-1];
                        cnt++;
                    }
                //}
                //else
                //{
                //    if (c[i - 1] != c[l - i])
                //    {
                //        c[l - i] = c[i - 1];
                //    }
                //}
            }
            Console.WriteLine(cnt);

        }
    }
}