import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    double L = (double)scan.nextInt();
    scan.close();

    System.out.println(String.format("%.12f", L*L*L/27));
  }
} import java.util.Scanner; Scanner java.util public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    double L = (double)scan.nextInt();
    scan.close();

    System.out.println(String.format("%.12f", L*L*L/27));
  }
} Main public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    double L = (double)scan.nextInt();
    scan.close();

    System.out.println(String.format("%.12f", L*L*L/27));
  } main {
    Scanner scan = new Scanner(System.in);
    double L = (double)scan.nextInt();
    scan.close();

    System.out.println(String.format("%.12f", L*L*L/27));
  } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) double L = (double)scan.nextInt(); L (double)scan.nextInt() scan.nextInt scan scan.close() scan.close scan System.out.println(String.format("%.12f", L*L*L/27)) System.out.println System.out System System.out String.format("%.12f", L*L*L/27) String.format String "%.12f" L*L*L/27 L*L*L L*L*L L L L 27 String[] args args public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    double L = (double)scan.nextInt();
    scan.close();

    System.out.println(String.format("%.12f", L*L*L/27));
  }
} public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    double L = (double)scan.nextInt();
    scan.close();

    System.out.println(String.format("%.12f", L*L*L/27));
  }
} Main
import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    double L = (double)scan.nextInt();
    scan.close();

    System.out.println(String.format("%.12f", L*L*L/27));
  }
}