import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int L = Integer.parseInt(in.next());
            double o = 0.000000;
            double w = 0.000000;
            double h = 0.000000;

            o = (double) L / 3.000000;
            w = (double) L / 3.000000;
            h = L - o - w;
            double ans = o * w * h;

            // 出力
            out.printf("%.12f%n", ans);

        }

    }
}
 import java.io.OutputStream; OutputStream java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.PrintWriter; PrintWriter java.io import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int L = Integer.parseInt(in.next());
            double o = 0.000000;
            double w = 0.000000;
            double h = 0.000000;

            o = (double) L / 3.000000;
            w = (double) L / 3.000000;
            h = L - o - w;
            double ans = o * w * h;

            // 出力
            out.printf("%.12f%n", ans);

        }

    }
} Main public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    } main {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    } InputStream inputStream = System.in; inputStream System.in System System.in OutputStream outputStream = System.out; outputStream System.out System System.out Scanner in = new Scanner(inputStream); in new Scanner(inputStream) PrintWriter out = new PrintWriter(outputStream); out new PrintWriter(outputStream) C solver = new C(); solver new C() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int L = Integer.parseInt(in.next());
            double o = 0.000000;
            double w = 0.000000;
            double h = 0.000000;

            o = (double) L / 3.000000;
            w = (double) L / 3.000000;
            h = L - o - w;
            double ans = o * w * h;

            // 出力
            out.printf("%.12f%n", ans);

        }

    } C public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int L = Integer.parseInt(in.next());
            double o = 0.000000;
            double w = 0.000000;
            double h = 0.000000;

            o = (double) L / 3.000000;
            w = (double) L / 3.000000;
            h = L - o - w;
            double ans = o * w * h;

            // 出力
            out.printf("%.12f%n", ans);

        } solve {
            // 入力
            int L = Integer.parseInt(in.next());
            double o = 0.000000;
            double w = 0.000000;
            double h = 0.000000;

            o = (double) L / 3.000000;
            w = (double) L / 3.000000;
            h = L - o - w;
            double ans = o * w * h;

            // 出力
            out.printf("%.12f%n", ans);

        } int L = Integer.parseInt(in.next()); L Integer.parseInt(in.next()) Integer.parseInt Integer in.next() in.next in double o = 0.000000; o 0.000000 double w = 0.000000; w 0.000000 double h = 0.000000; h 0.000000 o = (double) L / 3.000000 o (double) L / 3.000000 (double) L 3.000000 w = (double) L / 3.000000 w (double) L / 3.000000 (double) L 3.000000 h = L - o - w h L - o - w L - o - w L o w double ans = o * w * h; ans o * w * h o * w * h o w h out.printf("%.12f%n", ans) out.printf out "%.12f%n" ans int testNumber testNumber Scanner in in PrintWriter out out public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int L = Integer.parseInt(in.next());
            double o = 0.000000;
            double w = 0.000000;
            double h = 0.000000;

            o = (double) L / 3.000000;
            w = (double) L / 3.000000;
            h = L - o - w;
            double ans = o * w * h;

            // 出力
            out.printf("%.12f%n", ans);

        }

    }
} public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int L = Integer.parseInt(in.next());
            double o = 0.000000;
            double w = 0.000000;
            double h = 0.000000;

            o = (double) L / 3.000000;
            w = (double) L / 3.000000;
            h = L - o - w;
            double ans = o * w * h;

            // 出力
            out.printf("%.12f%n", ans);

        }

    }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int L = Integer.parseInt(in.next());
            double o = 0.000000;
            double w = 0.000000;
            double h = 0.000000;

            o = (double) L / 3.000000;
            w = (double) L / 3.000000;
            h = L - o - w;
            double ans = o * w * h;

            // 出力
            out.printf("%.12f%n", ans);

        }

    }
}

