#include <iostream>
using namespace std;

class A
{
 public:
    ~A() {}

    void const a() {}
};

class P
{
    public:

    int x;
    int y;

    P() : x(0), y(0) {}
    P(int x, int y) : x(x), y(y) {}

    
};
ostream& operator << (ostream& os, P p)
{
    os << "(" << p.x << "," << p.y << ")";
    return os;
}
class B : public A
{
    P p;
    public: 
    B(const P& p) : p(p) {}

    protected:
    void const b() 
    {
        cout << "B::p = " << p;
    }
};

class C : public B
{
    public:
    C(const P& p) : B(p) {}

    void const a() 
    {
        B::b();
    }
};



int main() 
{
    P p(19,20);
    cout << "p=" << p << endl;
    C c(p);
    cout << "c.a() liefert: ";
    c.a();
}