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;

class Program
{
  static void Main(string[] args)
  {
    var input = Console.ReadLine().ToCharArray();
    var count = 0;
    var charArray = "abcdefghijklmnopqrstuvwxyz".ToCharArray();

    for (int i = 0; i < input.Length; i++)
    {
      if (input[i] != input[input.Length - 1 - i])
      {
        for (int j = 0; j < charArray.Length; j++)
        {
          input[i] = charArray[j];
          if (input[i] == input[input.Length - 1 - i])
            break;
        }
        count++;
      }
    }

    Console.WriteLine(count);
  }
}