// derived classes

#include <iostream>
using namespace std;

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

class Rectangle: public Polygon {
  public:
    int area ()
      { return (width * height); }
  };

class Triangle: public Polygon {
  public:
    int area ()
      { return (width * height / 2); }
  };
  
int main () {
  Rectangle rect;
  Triangle trgl;
  rect.set_values (4,5);
  trgl.set_values (4,5);
  cout << "Rectangle area is " << rect.area() << endl;
  cout << "Triangle area is " << trgl.area() << endl;
  getchar();
  return 0;
}