#include <iostream>

using namespace std;

class Shape {
    public:
        virtual double getArea() = 0;
};
class Square : public Shape {
    private:
        double a;
    public:
        Square(double a){
            this->a = a;
        }
        virtual double getArea(){
            return a*a;
        }
};
class Circle : public Shape {
    private:
        double r;
    public:
        Circle(double r){
            this->r = r;
        }
        virtual double getArea(){
            return 3.14159265358979323846*r*r;
        }
};

void doSomething(Shape &r){
    cout << "We will compute the area" << endl;
    cout << "The area is " << r.getArea() << endl;
}


int main(){

    cout << "Let's compute area." << endl;

    Shape *s = NULL;

    cout << "1 for square, 0 for circle?" << endl;
    int x;
    cin >> x;

    if(x == 1){
        cout << "Great. Please enter edge length: " << endl;
        double edge;
        cin >> edge;
        s = new Square(edge);
    } else if(x == 0){
        cout << "Great. Please enter radius length: " << endl;
        double radius;
        cin >> radius;
        s = new Circle(radius);
    }

    if(s != NULL){
        doSomething(*s);
        delete s;
    }

    cout << "Good bye" << endl;
    return 0;
}