using System;

class superclass
{ private int x = 1;
  protected static int y = 1;
  public void f() 
   { Console.WriteLine("I'm the f in superclass\n"); }
  public virtual void g()
   { Console.WriteLine("I'm the g in superclass\n"); }
}

class subclass : superclass
{ public new int x = 1;
  public new void f()
   { Console.WriteLine("I'm the f in subclass\n"); }
  public override void g() 
   { x++;
     y++;
     Console.WriteLine("x is " + x + " and y is " + y); 
   }
}

public class goodquestion
{
  public static void Main(string[] args)
  {
     superclass A;  
     subclass B1;
     A = new subclass(); // A has different static and dynamic types
     B1 = new subclass();
     A.f();
     A.g();
     B1.f();
     B1 = (subclass)A; // why is this cast necessary, why is it valid?
     B1.f();
  }
}