import java.io.*;
import java.util.*;

public class Main
{
	public static void main(String[] args)
	{
		Scanner in = new Scanner(System.in);
		int L = in.nextInt();
		/*
		 let a, b, and c represent the side lengths
		 a + b + c = L
		 volume = a*b*c
		 according to the AM-GM inequality:
		 (a*b*c)^(1/3) <= (a+b+c)/3
		 (a*b*c)^(1/3) <= L/3
		 a*b*c <= (L/3)^3
		 */
		System.out.printf("%.15f\n", ((double)L*L*L)/27.0);
	}
} import java.io.*; io.* java import java.util.*; util.* java public class Main
{
	public static void main(String[] args)
	{
		Scanner in = new Scanner(System.in);
		int L = in.nextInt();
		/*
		 let a, b, and c represent the side lengths
		 a + b + c = L
		 volume = a*b*c
		 according to the AM-GM inequality:
		 (a*b*c)^(1/3) <= (a+b+c)/3
		 (a*b*c)^(1/3) <= L/3
		 a*b*c <= (L/3)^3
		 */
		System.out.printf("%.15f\n", ((double)L*L*L)/27.0);
	}
} Main public static void main(String[] args)
	{
		Scanner in = new Scanner(System.in);
		int L = in.nextInt();
		/*
		 let a, b, and c represent the side lengths
		 a + b + c = L
		 volume = a*b*c
		 according to the AM-GM inequality:
		 (a*b*c)^(1/3) <= (a+b+c)/3
		 (a*b*c)^(1/3) <= L/3
		 a*b*c <= (L/3)^3
		 */
		System.out.printf("%.15f\n", ((double)L*L*L)/27.0);
	} main {
		Scanner in = new Scanner(System.in);
		int L = in.nextInt();
		/*
		 let a, b, and c represent the side lengths
		 a + b + c = L
		 volume = a*b*c
		 according to the AM-GM inequality:
		 (a*b*c)^(1/3) <= (a+b+c)/3
		 (a*b*c)^(1/3) <= L/3
		 a*b*c <= (L/3)^3
		 */
		System.out.printf("%.15f\n", ((double)L*L*L)/27.0);
	} Scanner in = new Scanner(System.in); in new Scanner(System.in) int L = in.nextInt(); L in.nextInt() in.nextInt in System.out.printf("%.15f\n", ((double)L*L*L)/27.0) System.out.printf System.out System System.out "%.15f\n" ((double)L*L*L)/27.0 ((double)L*L*L) (double)L*L*L (double)L L L 27.0 String[] args args public class Main
{
	public static void main(String[] args)
	{
		Scanner in = new Scanner(System.in);
		int L = in.nextInt();
		/*
		 let a, b, and c represent the side lengths
		 a + b + c = L
		 volume = a*b*c
		 according to the AM-GM inequality:
		 (a*b*c)^(1/3) <= (a+b+c)/3
		 (a*b*c)^(1/3) <= L/3
		 a*b*c <= (L/3)^3
		 */
		System.out.printf("%.15f\n", ((double)L*L*L)/27.0);
	}
} public class Main
{
	public static void main(String[] args)
	{
		Scanner in = new Scanner(System.in);
		int L = in.nextInt();
		/*
		 let a, b, and c represent the side lengths
		 a + b + c = L
		 volume = a*b*c
		 according to the AM-GM inequality:
		 (a*b*c)^(1/3) <= (a+b+c)/3
		 (a*b*c)^(1/3) <= L/3
		 a*b*c <= (L/3)^3
		 */
		System.out.printf("%.15f\n", ((double)L*L*L)/27.0);
	}
} Main
import java.io.*;
import java.util.*;

public class Main
{
	public static void main(String[] args)
	{
		Scanner in = new Scanner(System.in);
		int L = in.nextInt();
		/*
		 let a, b, and c represent the side lengths
		 a + b + c = L
		 volume = a*b*c
		 according to the AM-GM inequality:
		 (a*b*c)^(1/3) <= (a+b+c)/3
		 (a*b*c)^(1/3) <= L/3
		 a*b*c <= (L/3)^3
		 */
		System.out.printf("%.15f\n", ((double)L*L*L)/27.0);
	}
}
