题解

#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
double r,d,c,s;
int main(){
    cin>>r;
    d=r*2;
    c=d*3.14159;
    s=r*r*3.14159;
    printf("%.4lf %.4lf %.4lf",d,c,s);
}