题解

#include<bits/stdc++.h>
using namespace std;
int main() {
	double r,pl = 3.14159;
	scanf("%lf",&r);
	printf("%.4lf",r * 2);
	cout << " ";
	printf("%.4lf",r * 2 * pl);
	cout << " ";
	printf("%.4lf",r * r * pl);
	return 0;
}