using System;

using System.IO;

public class Program

{

     public long GetLengthA(object o)

    {

        switch (o)

        {

            case Stream x:

                {

                    return x.Length;

                }

            case Array x: // <-- this is allowed

                {

                    return x.Length;

                }

        }

        return 0;

    }

    public long GetLengthB(object o)

    {

        if (o is Stream x)

        {

            return x.Length;

        }

        else if (o is Array y) 

        {

            return y.Length;

        }

        return 0;

    }

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}