using System;

public class Program

{

    public static void Main()

    {

        bool? test = null;

        Console.WriteLine(test == null);

        Console.WriteLine(test == true);

        Console.WriteLine(test == false);

        Console.WriteLine("-");

        test = true;

        Console.WriteLine(test == null);

        Console.WriteLine(test == true);

        Console.WriteLine(test == false);

        Console.WriteLine("-");

        test = false;

        Console.WriteLine(test == null);

        Console.WriteLine(test == true);

        Console.WriteLine(test == false);

    }

}