using System;

public class Program

{

    public static void Main()

    {

        new C().foo();

    }

    class A {

    public virtual void foo() {

        Console.WriteLine("A");

    }

}

​

class B : A {

    public override void foo() {

        Console.WriteLine("B");

    }

}

​

class C : B {

    static int i = 0;

    public override void foo() {

        i++;

        if(i > 3)

            throw new Exception("Overflow");

        (this as A).foo();

        Console.WriteLine("C");

    }

}

}