using System;

public class Program

{

    public static void Main()

    {

        test(0);

        test(1);

        test(2);

        test(3);

    }

​

    static void test(int val) {

        var res = (val == 1 ? 0 : val) switch {

            0 => A(), // 0 or 1

            2 => B(), // 2

            _ => throw new Exception()

        };

        Console.WriteLine("{0}: {1}", val, res);

    }

​

    static string A() { return "A"; }

    static string B() { return "B"; }

}