题解

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