class Cercle
{
	public double rayon;

	public Cercle(double r){
		rayon=r;
	}

	public Cercle(){
		rayon=3.45;
	}

	public double perimetre(){
		return 2*Math.PI*rayon;
	}

	public static void main(String[] args){
		Cercle c1 = new Cercle(6.1);
		Cercle c2 = new Cercle(2.7);
		Cercle c3 = new Cercle();

		System.out.printf("%f\n", c1.perimetre());
		System.out.printf("%f\n", c2.perimetre());
		System.out.printf("%f\n", c3.perimetre());
	}
}

class bob
{
	public static void main(String[] args){
		System.out.printf("%f\n", c1.perimetre());
		System.out.printf("%f\n", c2.perimetre());
		System.out.printf("%f\n", c3.perimetre());
	}
}