public class Main {
    public static void main(String[] args) {
        Shape circle = new Circle(5.0);
        Shape rectangle = new Rectangle(4.0, 6.0);
        Shape triangle = new Triangle(3.0, 8.0);

        ShapeUtil.printArea(circle);
        ShapeUtil.printArea(rectangle);
        ShapeUtil.printArea(triangle);
    }
}