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# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;
using System.Linq;
using System.Threading;

namespace ConsoleApp19
{
    class Program
    {
        static void Main(string[] args)
        {
            string s = Console.ReadLine();
            string r = string.Concat(s.Reverse());
            int count = 0;

            for (int i = 0;i < s.Length; i++)
            {
                for(int k=0; k < r.Length; k++)
                {
                    if (s[i] == r[k]) 
                    {
                        count++;
                    }
                }      
            }
            Console.WriteLine(count);
        }
    }
}