using System;
public class Program
{
class A{
}
class B : A{
class C{
public static void Main()
object b = new B();
object c = new C();
A a1 = b as A;
Console.WriteLine("1" + a1);
A a2 = (A)b;
Console.WriteLine("2" + a2);
A a3 = c as A;
Console.WriteLine("3" + a3);
A a4 = (A)c;
Console.WriteLine("4" + a4);