class Cercle
{
    private double rayon;

    static void bob(double r)
    {
        rayon=r;
    }

    static void bob()
    {
        rayon=3.45;
    }

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

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

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