using System;

class Base
{
    public Base()
    {
        Console.WriteLine("Base::Base");
        ((Derived)this).Foo();
    }
    public void Foo()
    {
        Console.WriteLine("Base::Foo");
    }
}
class Derived : Base
{
    public Derived()
    {
        Console.WriteLine("Derived::Derived");
    }
    public void Foo()
    {
        Console.WriteLine("Derived::Foo");
    }
}

public class Test
{
    public static void Main()
	{
		new Derived();
	}
}