#include <math.h>

struct Point
{
    double x, y;
};


class Figure
{
    protected:
    double l2(double x1, double y1, double x2, double y2)
    {
        return sqrt((x2 - x1)*(x2 - x1) + (y2 - y1)*(y2 - y1)); 
    }

    public:
    virtual double calc_area() = 0;
    virtual double calc_perimiter() = 0;
    virtual void name() = 0;
};