import java.util.*;

class Main {

    static public double solve(int L) {
        return Math.pow(L/3.0, 3);
    }

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

        int L = sc.nextInt();

        sc.close();

        System.out.println(String.format("%.7f", solve(L)));
    }
} import java.util.*; util.* java class Main {

    static public double solve(int L) {
        return Math.pow(L/3.0, 3);
    }

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

        int L = sc.nextInt();

        sc.close();

        System.out.println(String.format("%.7f", solve(L)));
    }
} Main static public double solve(int L) {
        return Math.pow(L/3.0, 3);
    } solve {
        return Math.pow(L/3.0, 3);
    } return Math.pow(L/3.0, 3); Math.pow(L/3.0, 3) Math.pow Math L/3.0 L 3.0 3 int L L public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int L = sc.nextInt();

        sc.close();

        System.out.println(String.format("%.7f", solve(L)));
    } main {
        Scanner sc = new Scanner(System.in);

        int L = sc.nextInt();

        sc.close();

        System.out.println(String.format("%.7f", solve(L)));
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int L = sc.nextInt(); L sc.nextInt() sc.nextInt sc sc.close() sc.close sc System.out.println(String.format("%.7f", solve(L))) System.out.println System.out System System.out String.format("%.7f", solve(L)) String.format String "%.7f" solve(L) solve L String[] args args
import java.util.*;

class Main {

    static public double solve(int L) {
        return Math.pow(L/3.0, 3);
    }

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

        int L = sc.nextInt();

        sc.close();

        System.out.println(String.format("%.7f", solve(L)));
    }
}