using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("--");

        Console.WriteLine("|-> " + string.Join(" ", new object[] { null, "a", null, "b"}) );

        Console.WriteLine("|-> " + string.Join(" ", new string[] { null, "a", null, "b"}) );

        Console.WriteLine("|-> " + string.Join(" ", new object[] { null, 'a', null, 'b'}) );

        Console.WriteLine("|-> " + string.Join(" ", new object[] { ((char?)null), 'a', null, 'b'}) );

        Console.WriteLine("--");

    }

}