#include <iostream>
 
class Punkt
{
  int _x, _y;
public:
  Punkt(int x, int y)
  : _x(x), _y(y)
  {
  }
 
  virtual ~Punkt() {}
protected:
  virtual void print(std::ostream& os) const
  {
    os << '(' << _x << ',' << _y << ')';
  }
private:    
  friend std::ostream& operator<<(std::ostream& os, Punkt const& p);
};
 
std::ostream& operator<<(std::ostream& os, Punkt const& p)
{
  p.print(os);
  return os;
}   
 
int main()
{
  Punkt p(4,2);
  std::cout << "Punkt P" << p << '\n';
}