using System;

public class A

{

    public virtual void log()

    {

        Console.WriteLine("A");

    }

}

​

public class B : A 

{

}

​

public class C : B

{

    public override void log()

    {

        Console.WriteLine("C");

    }

}

​

public class Program

{

    public static void Main()

    {

        new B().log();

        new A().log();

        new C().log();

        Console.WriteLine("Hello World");

    }

}