题解

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