using System;

public class Program

{

    public static void Main()

    {

        bool? isMonday = null;

        if (isMonday == true)

        {

            Console.WriteLine("Na Lukas, schönes Wochenende gehabt?");

        }       

        if ((bool)isMonday)

        {

            Console.WriteLine("Na Lukas, schönes Wochenende gehabt?");

        }       

    }

}