using System;

public class Program

{

    public static void Main()

    {

        var ex1 = "tset";

        var ex2 = "121";

        var ex3 = "321";

        Console.WriteLine(Reverse("test") == ex1);

        Console.WriteLine(Reverse("121") == ex2);

        Console.WriteLine(Reverse("111") == ex2);

        Console.WriteLine(Reverse("123") == ex3);

    }

    private static string Reverse(string arg) 

    {

        // IMPLEMENT ME but don't use built in method

        return "";

    }

}