小题解

#include<bits/stdc++.h>
using namespace std;
int main(){
    double n;
    cin>>n;
    cout<<setprecision(4)<<fixed<<n*2;
    cout<<" ";
    cout<<setprecision(4)<<fixed<<n*2*3.14159;
    cout<<" ";
    cout<<setprecision(4)<<fixed<<n*n*3.14159;
    return 0;
}