import java.util.*;
class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    System.out.println(L*L*L/27);
  }
} import java.util.*; util.* java class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    System.out.println(L*L*L/27);
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    System.out.println(L*L*L/27);
  } main {
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    System.out.println(L*L*L/27);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double L = sc.nextDouble(); L sc.nextDouble() sc.nextDouble sc System.out.println(L*L*L/27) System.out.println System.out System System.out L*L*L/27 L*L*L L*L*L L L L 27 String[] args args
import java.util.*;
class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    double L = sc.nextDouble();
    System.out.println(L*L*L/27);
  }
}
