// abstract classes

abstract class A {
	protected int i;
	public void m() {i=20;}
	public abstract int n();
}


class B extends A {

public int n() {return i;}

}


class AbstractTest {

public static void main (String args[]) {

	B b = new B ();
	
	A a = b;

	a.m();
	int x = a.n();

	System.out.println(x);

}

}