加油！

#include <iostream>
using namespace std;
int main(){
double r,PI=3.14159;
double a,b,s;
cin>>r;
a=r2;
b=r2PI;
s=rr*PI;
printf("%.4f",a);
cout <<" ";
printf("%.4f",b);
cout <<" ";
printf("%.4f",s);
return 0;
}