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 line = Console.ReadLine().Trim();
    char[] array = line.ToCharArray();
    
    int count = 0;
    for (int i = 0; i < array.Length / 2; i++)
    {
      if (line[i] == array[array.Length - 1 - i]) continue;
      array[array.Length - 1 - i] = line[i];
      count++;
    }
    
    Console.WriteLine(count);
  }
}