public class Circulo extends Figura{
    private static final double PI=3.141618;

    private double raio;

    public Circulo(){
	super(1);
	raio=1;
    }

    public Circulo(double r){
	raio=(r<0)?1:r;
    }

    public double raio(){
	return raio;
    }

    public double area(){
	return PI*raio*raio;
    }

    public double perimetro(){
	return 2*PI*raio;
    }
}