题解

#include<iostream>
using namespace std;

int main(){
double r;
cin>>r;
double t=2r;
double c=23.14159r;
double s=3.14159r*r;
printf("%.4lf",t);
cout<<" ";
printf("%.4lf",c);
cout<<" ";
printf("%.4lf",s);
return 0;
}