// derived classes
#include <iostream.h>

class CPolygon {
protected:
    int width, height;
public:
    void set_values (int a, int b)
    { width=a; height=b;}
};

class CRectangle: public CPolygon {
public:
    int area (void)
    { return (width * height); }
};

class CTriangle: public CPolygon {
public:
    int area (void)
    { return (width * height / 2); }
};
  
int main () {
  CRectangle rect;
  CTriangle trgl;
  rect.set_values (4,5);
  trgl.set_values (4,5);
  cout << rect.area() << endl;
  cout << trgl.area() << endl;
  return 0;
}