//:co7:RTTI.java
import java.util.*;
class Useful
{
	public void f(){System.out.println("f");}
	public void g(){System.out.println("g");}
}
class MoreUseful extends Useful
{
	public void f(){System.out.println("f2");}
	public void g(){System.out.println("g2");}
	public void u(){System.out.println("u");}
	
}
public class RTTI
{
public static void main(String [] args)
{
	Useful []x={ new Useful(),new MoreUseful()};
	x[0].f();
	x[1].g();
	//x[1].u();
	//((MoreUseful)x[0]).u();
	
	
}
}