非常简单

//#include<iostream>
#include<cstdio>
//#include<algorithm>
//#include<cmath>
using namespace std;
const double Pi=3.14159;
int main()
{
double r;
scanf("%lf",&r);
printf("%.4lf %.4lf %.4lf",2r,2rPi,Pir*r);
return 0;
}