/*package whatever //do not write package name here */

import java.io.*;
import java.util.*;
public class Main {
	public static void main (String[] args) {
		Scanner input = new Scanner(System.in);
		double n = input.nextDouble();
		double ans = (n*n*n)/27.0;
		System.out.printf("%.12f",ans);
		
	}
} import java.io.*; io.* java import java.util.*; util.* java public class Main {
	public static void main (String[] args) {
		Scanner input = new Scanner(System.in);
		double n = input.nextDouble();
		double ans = (n*n*n)/27.0;
		System.out.printf("%.12f",ans);
		
	}
} Main public static void main (String[] args) {
		Scanner input = new Scanner(System.in);
		double n = input.nextDouble();
		double ans = (n*n*n)/27.0;
		System.out.printf("%.12f",ans);
		
	} main {
		Scanner input = new Scanner(System.in);
		double n = input.nextDouble();
		double ans = (n*n*n)/27.0;
		System.out.printf("%.12f",ans);
		
	} Scanner input = new Scanner(System.in); input new Scanner(System.in) double n = input.nextDouble(); n input.nextDouble() input.nextDouble input double ans = (n*n*n)/27.0; ans (n*n*n)/27.0 (n*n*n) n*n*n n n n 27.0 System.out.printf("%.12f",ans) System.out.printf System.out System System.out "%.12f" ans String[] args args public class Main {
	public static void main (String[] args) {
		Scanner input = new Scanner(System.in);
		double n = input.nextDouble();
		double ans = (n*n*n)/27.0;
		System.out.printf("%.12f",ans);
		
	}
} public class Main {
	public static void main (String[] args) {
		Scanner input = new Scanner(System.in);
		double n = input.nextDouble();
		double ans = (n*n*n)/27.0;
		System.out.printf("%.12f",ans);
		
	}
} Main
/*package whatever //do not write package name here */

import java.io.*;
import java.util.*;
public class Main {
	public static void main (String[] args) {
		Scanner input = new Scanner(System.in);
		double n = input.nextDouble();
		double ans = (n*n*n)/27.0;
		System.out.printf("%.12f",ans);
		
	}
}