using System;
public class Program
{
public static void Main()
var a = new A();
var b = new B();
a.Speak();
b.Speak();
a.Speak2();
b.Speak2();
}
public class A
public virtual void Speak()
Console.WriteLine("A");
public void Speak2()
Speak();
public class B : A
public override void Speak()
Console.WriteLine("B");