class LFRPoint
{
private:
    /* data */
public:
    double x, y;
    LFRPoint(/* args */);
    LFRPoint(double x, double y);
    ~LFRPoint();

    LFRPoint operator-(const LFRPoint& pt){return LFRPoint(x-pt.x, y-pt.y);}
    LFRPoint operator+(const LFRPoint& pt){return LFRPoint(x+pt.x, y+pt.y);}
};

class LFRVector : public LFRPoint
{
private:
    /* data */
public:
    LFRVector(/* args */);
    LFRVector(double x, double y);
    LFRVector(const LFRPoint& pt);
    ~LFRVector();

};

class LFRLine
{
private:
    /* data */

public:
    LFRPoint start;
    LFRVector dir;

    LFRLine(/* args */);
    LFRLine(LFRPoint start, LFRVector dir);
    LFRLine(LFRPoint start, LFRPoint end);
    ~LFRLine();
};