using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Reverse("string"));

    }

    public static string Reverse(string str)

    {

        char[] charArray = str.ToCharArray();

        int l = str.Length -1;

        for (int i = 0 ; i < l; i++, l--)

        {

            charArray[l] ^= charArray[i];

            charArray[l] ^= charArray[i];

            charArray[l] ^= charArray[i];

        }

        return new string(charArray);

    }

}