import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a = scan.nextInt();
    long b = a*a*a;

    System.out.println((double) b/27);
  }
} import java.util.*; util.* java public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a = scan.nextInt();
    long b = a*a*a;

    System.out.println((double) b/27);
  }
} Main public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a = scan.nextInt();
    long b = a*a*a;

    System.out.println((double) b/27);
  } main {
    Scanner scan = new Scanner(System.in);
    int a = scan.nextInt();
    long b = a*a*a;

    System.out.println((double) b/27);
  } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int a = scan.nextInt(); a scan.nextInt() scan.nextInt scan long b = a*a*a; b a*a*a a*a*a a a a System.out.println((double) b/27) System.out.println System.out System System.out (double) b/27 (double) b 27 String[] args args public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a = scan.nextInt();
    long b = a*a*a;

    System.out.println((double) b/27);
  }
} public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a = scan.nextInt();
    long b = a*a*a;

    System.out.println((double) b/27);
  }
} Main
import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int a = scan.nextInt();
    long b = a*a*a;

    System.out.println((double) b/27);
  }
}
