题解

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