class electrical_part
{
public:
    electrical_part(double price):_price(price) {};

    virtual double get_price() const
    {
        return _price;
    };
    virtual void print() const = 0;

protected:
    double _price;
};


class button: virtual public electrical_part
{
public:
    button():electrical_part(2) {};

    void print() const override
    {
        std::cout << "Button: " << _price << std::endl;
    };
};

class light_bulb: virtual public electrical_part
{
public:
    light_bulb():electrical_part(3.5) {};
    void print() const override
    {
        std::cout << "Light bulb: " << _price << std::endl;
    };
};

class desk_lamp: public button, public light_bulb
{
public:
    desk_lamp():electrical_part(6) {};

    void print() const override
    {
        std::cout << "Desk lamp: " << _price << std::endl;
    };
};