import java.util.Scanner;
import java.io.PrintWriter;

class Main {
    static String maxVolume(int l) {
        double vol = l * l * l / 27.0;

        return String.format("%.12f", vol);
    }


    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        int l = Integer.parseInt(sc.next());

        out.println(maxVolume(l));
        out.flush();
    }
} import java.util.Scanner; Scanner java.util import java.io.PrintWriter; PrintWriter java.io class Main {
    static String maxVolume(int l) {
        double vol = l * l * l / 27.0;

        return String.format("%.12f", vol);
    }


    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        int l = Integer.parseInt(sc.next());

        out.println(maxVolume(l));
        out.flush();
    }
} Main static String maxVolume(int l) {
        double vol = l * l * l / 27.0;

        return String.format("%.12f", vol);
    } maxVolume {
        double vol = l * l * l / 27.0;

        return String.format("%.12f", vol);
    } double vol = l * l * l / 27.0; vol l * l * l / 27.0 l * l * l l * l * l l l l 27.0 return String.format("%.12f", vol); String.format("%.12f", vol) String.format String "%.12f" vol int l l public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        int l = Integer.parseInt(sc.next());

        out.println(maxVolume(l));
        out.flush();
    } main {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        int l = Integer.parseInt(sc.next());

        out.println(maxVolume(l));
        out.flush();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) PrintWriter out = new PrintWriter(System.out); out new PrintWriter(System.out) int l = Integer.parseInt(sc.next()); l Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc out.println(maxVolume(l)) out.println out maxVolume(l) maxVolume l out.flush() out.flush out String[] args args
import java.util.Scanner;
import java.io.PrintWriter;

class Main {
    static String maxVolume(int l) {
        double vol = l * l * l / 27.0;

        return String.format("%.12f", vol);
    }


    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        int l = Integer.parseInt(sc.next());

        out.println(maxVolume(l));
        out.flush();
    }
}
