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 ConsoleApp1
{
    static class BPalindromephilia
    {
        static void Main(string[] args)
        {
            var s = Console.ReadLine();
            var harf1 = s.Substring(0, s.Length / 2).ToCharArray();
            var harf2 = s.Length % 2 == 0 ? 
                s.Substring(s.Length / 2).Reverse().ToArray() :
                s.Substring(s.Length / 2 + 1).Reverse().ToArray();

            int count = 0;
            for (int i = 0; i < s.Length / 2; i++)
            {
                if (harf1[i] != harf2[i])
                {
                    count++;
                }
            }

            Console.WriteLine(count);
            Console.ReadLine();
        }
    }
}