import java.util.*;
import java.io.PrintWriter;
import static java.lang.Integer.*;
import static java.lang.Long.*;
import static java.lang.Math.*;
import static java.lang.System.*;

public class Main {
	public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int l = parseInt(sc.next());
		sc.close();
		double ll = (double)l/3;
		out.printf("%.12f%n", ll*ll*ll);
	}
} import java.util.*; util.* java import java.io.PrintWriter; PrintWriter java.io import static java.lang.Integer.*; import static java.lang.Integer.*; import static java.lang.Integer.*; import static java.lang.Long.*; import static java.lang.Long.*; import static java.lang.Long.*; import static java.lang.Math.*; import static java.lang.Math.*; import static java.lang.Math.*; import static java.lang.System.*; import static java.lang.System.*; import static java.lang.System.*; public class Main {
	public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int l = parseInt(sc.next());
		sc.close();
		double ll = (double)l/3;
		out.printf("%.12f%n", ll*ll*ll);
	}
} Main public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int l = parseInt(sc.next());
		sc.close();
		double ll = (double)l/3;
		out.printf("%.12f%n", ll*ll*ll);
	} main {
		int i,j;
		Scanner sc = new Scanner(in);
		int l = parseInt(sc.next());
		sc.close();
		double ll = (double)l/3;
		out.printf("%.12f%n", ll*ll*ll);
	} int i i j; j Scanner sc = new Scanner(in); sc new Scanner(in) int l = parseInt(sc.next()); l parseInt(sc.next()) parseInt sc.next() sc.next sc sc.close() sc.close sc double ll = (double)l/3; ll (double)l/3 (double)l 3 out.printf("%.12f%n", ll*ll*ll) out.printf out "%.12f%n" ll*ll*ll ll*ll*ll ll ll ll String[] args args public class Main {
	public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int l = parseInt(sc.next());
		sc.close();
		double ll = (double)l/3;
		out.printf("%.12f%n", ll*ll*ll);
	}
} public class Main {
	public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int l = parseInt(sc.next());
		sc.close();
		double ll = (double)l/3;
		out.printf("%.12f%n", ll*ll*ll);
	}
} Main
import java.util.*;
import java.io.PrintWriter;
import static java.lang.Integer.*;
import static java.lang.Long.*;
import static java.lang.Math.*;
import static java.lang.System.*;

public class Main {
	public static void main(String[] args) {
		int i,j;
		Scanner sc = new Scanner(in);
		int l = parseInt(sc.next());
		sc.close();
		double ll = (double)l/3;
		out.printf("%.12f%n", ll*ll*ll);
	}
}
