using System;

​

public class Program

{

    public static void Main()

    {

        int? a = 1;

        if (a is not 2 or 3)

        {

            Console.WriteLine("Hello 1");

        }

        else

        {

            Console.WriteLine("Hello 2");

        }

​

        if (a is not 2 or 1)

        {

            Console.WriteLine("Hello 1");

        }

        else

        {

            Console.WriteLine("Hello 2");

        }

​

        if (a is not 2 or not 1)

        {

            Console.WriteLine("Hello 1");

        }

        else

        {

            Console.WriteLine("Hello 2");

        }

    }

}