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;
 
namespace Sample
{
  class Sample
  {
    static void Main(string[] args)
    {
    string str =Console.ReadLine();
      int N=str.Length;
      int ans=0;

        for(int i=0;i<=(N/2-1);i++){
          if(str.Substring(i,1)!=str.Substring(N-1-i,1)){
            ans+=1;
          }
        }
      Console.WriteLine(ans);
      
    }
    
  }

}