import java.util.*;
import java.util.Map.Entry;
 
class Main {
	 static int mod =  (int) (Math.pow(10,9)+7);
//	 static int mod = 998244353;
	 public static void main(String[] args) {
	        Scanner sc = new Scanner(System.in);
	        double L = sc.nextDouble();
	        double a=L/3/3/3*L*L;
	        System.out.println(a);
	 }
} import java.util.*; util.* java import java.util.Map.Entry; Entry java.util.Map class Main {
	 static int mod =  (int) (Math.pow(10,9)+7);
//	 static int mod = 998244353;
	 public static void main(String[] args) {
	        Scanner sc = new Scanner(System.in);
	        double L = sc.nextDouble();
	        double a=L/3/3/3*L*L;
	        System.out.println(a);
	 }
} Main static int mod =  (int) (Math.pow(10,9)+7); mod (int) (Math.pow(10,9)+7) Math.pow(10,9) Math.pow Math 10 9 7 //	 static int mod = 998244353;
	 public static void main(String[] args) {
	        Scanner sc = new Scanner(System.in);
	        double L = sc.nextDouble();
	        double a=L/3/3/3*L*L;
	        System.out.println(a);
	 } main {
	        Scanner sc = new Scanner(System.in);
	        double L = sc.nextDouble();
	        double a=L/3/3/3*L*L;
	        System.out.println(a);
	 } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double L = sc.nextDouble(); L sc.nextDouble() sc.nextDouble sc double a=L/3/3/3*L*L; a L/3/3/3*L*L L/3/3/3*L*L L/3/3/3 3 L/3/3/3 L 3 3 3 L L System.out.println(a) System.out.println System.out System System.out a String[] args args
import java.util.*;
import java.util.Map.Entry;
 
class Main {
	 static int mod =  (int) (Math.pow(10,9)+7);
//	 static int mod = 998244353;
	 public static void main(String[] args) {
	        Scanner sc = new Scanner(System.in);
	        double L = sc.nextDouble();
	        double a=L/3/3/3*L*L;
	        System.out.println(a);
	 }
}