class Circle : Shape
    {

        public double r = 50.0;  // radius

        public Circle(double radius)  {r=radius;}
        
        public double area_of() { return Math.PI * r * r; }

        public override double area_of_overlap(Circle other)
        {
            double distance_squared;
            double chord_area;
            double h;

            if (equals(other)) return area_of();

            distance_squared = Math.Pow(x - other.x, 2.0) + Math.Pow(y - other.y, 2.0);

            if (distance_squared >= 4 * r * r)
                return 0.0;
            else
            {
                h = (2.0 * r - Math.Sqrt(distance_squared)) / 2.0;
                chord_area = (r * r * Math.Acos((r - h) / r)) - (r - h) * Math.Sqrt(2 * r * h - h * h);
                return 2 * chord_area;
            }
        }

        public Object Clone()
        {
            Circle copyOfMe = new Circle();
            copyOfMe.move(x, y);
            copyOfMe.niche_count = niche_count;
            return copyOfMe;
        }

    }