题解

#include<iostream>
#include<cstdio>
int main(){
    double a;
    std::cin>>a;
    printf("%.4f",a*2);
    std::cout<<" ";
    printf("%.4f",a*2*3.14159);
    std::cout<<" ";
    printf("%.4f",a*a*3.14159);
    return 0;
}