What is the output:

using System;
class A
{
    public virtual void Y()
    {
    // Used when C is referenced through A.
    Console.WriteLine("A.Y");
    }
}
class B : A
{
    public override void Y()
    {
    // Used when B is referenced through A.
    Console.WriteLine("B.Y");
    }
}
class C : A
{
    public void Y() // Can be "new public void Y()"
    {
    // Not used when C is referenced through A.
    Console.WriteLine("C.Y");
    }
}
class Program
{
    static void Main()
    {
    // Reference B through A.
    A ab = new B();
    ab.Y();

    // Reference C through A.
    A ac = new C();
    ac.Y();
    }
}