class point
{
friend class triangle;
friend bool point_eq(point & a, point & b);
public:
    point();
    point(double x, double y);
    double x() const;
    double y() const;
    double distance(point & p) const;
private:
    double my_x;
    double my_y;
};

class triangle
{
public:
    triangle();
    triangle(point a, point b, point c);
    point p1();
    point p2();
    point p3();
    double area();
    point center();
    void shift(point v);

private:
    point my_p1;
    point my_p2;
    point my_p3;
};