import java.util.Scanner;

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

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int l = sc.nextInt();
		double ans;
		ans = ((double)l/3) * ((double)l/3) * ((double)l/3);
		System.out.println(ans);
	}
}
