import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double max = Math.pow((double)N/3, 3); 
		
		System.out.println(max);
		
	}

} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double max = Math.pow((double)N/3, 3); 
		
		System.out.println(max);
		
	}

} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double max = Math.pow((double)N/3, 3); 
		
		System.out.println(max);
		
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double max = Math.pow((double)N/3, 3); 
		
		System.out.println(max);
		
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc double max = Math.pow((double)N/3, 3); max Math.pow((double)N/3, 3) Math.pow Math (double)N/3 (double)N 3 3 System.out.println(max) System.out.println System.out System System.out max String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double max = Math.pow((double)N/3, 3); 
		
		System.out.println(max);
		
	}

} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double max = Math.pow((double)N/3, 3); 
		
		System.out.println(max);
		
	}

} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double max = Math.pow((double)N/3, 3); 
		
		System.out.println(max);
		
	}

}