Write class shape with width and height following a constructor that gives value to them.
Then define two sub-classes triangle and rectangle.
Those sub-classes can calculate the area of the shape area().
You need to follow the main() below. Please complete the program.
int main (){
    Rectangle rect;
    Triangle tri;
    rect.set_data (5,3);
    tri.set_data (2,5);
    cout << rect.area() << ";" << tri.area() << endl;
    return 0;
}