import java.util.Scanner;
public class Main{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        double radius = in.nextDouble();
        double pi = 3.1415926;
        double volume = 4 * pi * Math.pow(radius, 3) / 3;
        System.out.printf("%.3f", volume);
    }
}