using System;

public class Program

{

    public static void Main()

    {

        BadRobot robot = null;

        if (robot != null)

        {

            Console.WriteLine("Oh no!");

        }

        else

        {

            Console.WriteLine("Phew!");

        }

        if (robot is not null)

        {

            Console.WriteLine("Oh no! x2");

        }

        else

        {

            Console.WriteLine("Phew! x2");

        }

    }

}

​

class BadRobot

{

    public static bool operator ==(BadRobot left, BadRobot right)

    {

        return false;

    }

    public static bool operator !=(BadRobot left, BadRobot right)

    {

        return true;

    }

}