abstract class Area{
    public abstract double draw();
}
class circle extends Area{
    double r;
    public double draw() {
        double area = 3.14 * r * r;
        System.out.println(area);
        return area;
    }
}
class rectangle extends Area{
    double l,b;
    public double draw() {
        double area = l * b;
        System.out.println(area);
        return area;
    }
}
class tangle extends Area{
    double b,h;
    public double draw() {
        double area = 0.5 * b * h;
        System.out.println(area);
        return area;
    }
}
public class Main{
    static void main(String[] args) {
        circle c=new circle();
        c.r=5;
        c.draw();
        rectangle a=new rectangle();
        a.l=5;
        a.b=4;
        a.draw();
        tangle t=new tangle();
        t.b=5;
        t.h=4;
        t.draw();
    }
}