class  point
{
public:
   point();                         // set coordinate to (0,0)
   point(double x, double y);       // set coordinate to (x,y)
   void set_x(double x);            // Set the priviate variable my_x
   void set_y(double y);            // Set the priviate variable my_y
   double get_x();                  // Access the priviate variable my_x
   double get_y();				    // Access the priviate variable my_y
   double distance(point p);        // computer the distance to point p
   double from_org();               // computer the distance to the origin   
   void shift(point v);             // shift v 
private:
   double my_x;                     // coordinate x
   double my_y;                     // coordinate y
   double diff(double x, double y); // this is just a helper
};