class derivative of one class and base of another

class b1
{
public:
    b1() { }
    ~b1() { }
    virtual void saida() { cout << "b1" << endl; }
};

class base : public b1
{
public:
    base() { }
    ~base() { }
    virtual void saida() { cout << "base" << endl; }
};

class derivada : public base
{
public:
    derivada() { }
    ~derivada() { }

    void saida() { cout << "derivada" << endl; b1::saida(); }
};


int main() {

    base* b = new derivada;

    b->saida();

    return 0;
}