#include <iostream>
#include <cstdlib>
using namespace std;

class base {
	int i;
protected:
	virtual void print(ostream& ost) const {ost << i;}
public:
	base(int initial_i): i(initial_i) {}
	virtual ~base() {}

	friend ostream& operator<<(ostream& ost, const base& b) {
		b.print(ost);
		return ost;
	}
};

class derived: public base {
	int j;
	void print(ostream& ost) const {base::print(ost); ost << ", " << j;}
public:
	derived(int initial_i, int initial_j): base(initial_i), j(initial_j) {}
};

int main()
{
	base b(10);
	const base *p = &b;
	cout << *p << "\n";   //operator<<(cout, *p) << "\n";

	derived d(20, 30);
	p = &d;
	cout << *p << "\n";   //operator<<(cout, *p) << "\n";

	return EXIT_SUCCESS;
}