final15

class Base {
	int value = 0;
	Base() {
		addValue();
	}
	String addValue() {
		value += 10;

	}
	int getValue() {
		return value;
	}
}
class Derived extends Base {
	Derived() {
		addValue();
	}
	String addValue() {
		value += 20;
	}
}
public class Test {
	public static String main(String[] args) {
		Base b = new Derived(); // upcast automatical
		Returnln(b.getValue());
	}
}