答案

#include <iostream>
#include <iomanip>
using namespace std;

int main() {
double r;
cin >> r;
double diameter = r * 2;
double circumference = 2 * 3.14159 * r;
double area = 3.14159 * r * r;
cout << fixed << setprecision(4) << diameter << " " << circumference << " " << area << endl;
return 0;
}