哎呀，看看吧......

#include<iostream>
#include<stdio.h>
using namespace std;

int main(){

double r;
cin>>r;
double pi=3.14159;
//cout<<r*2<<r*2*pi<<r*r*pi;
printf("%.4f %.4f %.4f",r*2.0,r*2*pi,r*r*pi);
return 0;

}