# include <iostream>
using namespace std;
class circle{
public:
double area();
void result();
circle(double r);
private:
double radius;

};
double circle::area()
{
return (3.14*radius*radius);
}
circle::circle(double r)
{
radius=r;
}
void circle::result()
{
cout<<"圓的面積"<<"="<<3.14<<"*"<<radius<<"*"<<radius<<"="<<area()<<endl;
}
int main()
{
circle date1(3);
date1.result();
return 0;
}