#include 
using namespace std;

const double PI = 3.1415;

class Circle {
public:
  void print_area() const;
  void set_area(const double &radius);

private:
  double area;

};

void Circle::print_area() const {
     cout << "Area: " << area 
          << endl;
}

void Circle::set_area(const double &radius) {
  area = PI * radius * radius;
}

int main() {
  Circle c;
  double radius;

  cin >> radius;

  c.set_area(radius);
  c.print_area();
  return 0;
}