import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    double ans = (L / (double)3) * (L / (double)3) * (L / (double)3);
    System.out.println(ans);
  }
} import java.util.*; util.* java public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    double ans = (L / (double)3) * (L / (double)3) * (L / (double)3);
    System.out.println(ans);
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    double ans = (L / (double)3) * (L / (double)3) * (L / (double)3);
    System.out.println(ans);
  } main {
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    double ans = (L / (double)3) * (L / (double)3) * (L / (double)3);
    System.out.println(ans);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double L = sc.nextDouble(); L sc.nextDouble() sc.nextDouble sc double ans = (L / (double)3) * (L / (double)3) * (L / (double)3); ans (L / (double)3) * (L / (double)3) * (L / (double)3) (L / (double)3) * (L / (double)3) * (L / (double)3) (L / (double)3) L (double)3 (L / (double)3) L (double)3 (L / (double)3) L (double)3 System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    double ans = (L / (double)3) * (L / (double)3) * (L / (double)3);
    System.out.println(ans);
  }
} public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    double ans = (L / (double)3) * (L / (double)3) * (L / (double)3);
    System.out.println(ans);
  }
} Main
import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    double ans = (L / (double)3) * (L / (double)3) * (L / (double)3);
    System.out.println(ans);
  }
}