private static boolean intersect (Circle c1, Circle c2){
		double x=Math.pow((c1.center_x - c2.center_x),2);
	    double y=Math.pow((c1.center_y - c2.center_y),2);
	    double res=Math.sqrt(x+y);
		return (res<(c1.radius+c2.radius) || res<Math.abs(c1.radius-c2.radius));
	}