#include
using namespace std;
class Circle
{
public:
Circle(double r=0):radius(r){}
double Area(){ return 3.14 * radius * radius; }
friend double Perimeter(const Circle &c);
private:
double radius;
};
double Perimeter(const Circle &c)
{
return 2.* 3.14 * c.radius;
}
int main()
{
Circle a(10.);
cout