#include <iostream>
#include <memory>
#include <vector>
class Shape {
public:
 virtual double area() const = 0;
 virtual void displayName() const = 0;
 virtual ~Shape() = default;
};
class Rectangle : public Shape {
private:
 double length;
 double width;
public:
 Rectangle(double givenLength, double givenWidth)
 : length(givenLength), width(givenWidth) {}
 double area() const override {
 return length * width;
 }
 void displayName() const override {
 std::cout << "Rectangle";
 }
};
class Circle : public Shape {
private:
 double radius;
public:
 explicit Circle(double givenRadius) : radius(givenRadius) {}
 double area() const override {
 constexpr double PI = 3.141592653589793;
 return PI * radius * radius;
 }
 void displayName() const override {
 std::cout << "Circle";
 }
};
int main() {
 std::vector<std::unique_ptr<Shape>> shapes;
 shapes.push_back(std::make_unique<Rectangle>(5.0, 3.0));
 shapes.push_back(std::make_unique<Circle>(2.0));
 for (const auto& shape : shapes) {
 shape->displayName();
 std::cout << " Area: " << shape->area() << '\n';
 }
 return 0;
}