import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

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

    static class CMaximumVolume {
        public void solve(int testNumber, inputClass sc, PrintWriter out) {
            double L = sc.nextDouble();
            BigDecimal a = BigDecimal.valueOf(L / 3);
            out.println(a.multiply(a).multiply(a).toPlainString());
        }

    }

    static class inputClass {
        BufferedReader br;
        StringTokenizer st;

        public inputClass(InputStream in) {

            br = new BufferedReader(new InputStreamReader(in));
        }

        public String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }

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

    static class CMaximumVolume {
        public void solve(int testNumber, inputClass sc, PrintWriter out) {
            double L = sc.nextDouble();
            BigDecimal a = BigDecimal.valueOf(L / 3);
            out.println(a.multiply(a).multiply(a).toPlainString());
        }

    }

    static class inputClass {
        BufferedReader br;
        StringTokenizer st;

        public inputClass(InputStream in) {

            br = new BufferedReader(new InputStreamReader(in));
        }

        public String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }

    }
} Main public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        inputClass in = new inputClass(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        CMaximumVolume solver = new CMaximumVolume();
        solver.solve(1, in, out);
        out.close();
    } main {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        inputClass in = new inputClass(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        CMaximumVolume solver = new CMaximumVolume();
        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 inputClass in = new inputClass(inputStream); in new inputClass(inputStream) PrintWriter out = new PrintWriter(outputStream); out new PrintWriter(outputStream) CMaximumVolume solver = new CMaximumVolume(); solver new CMaximumVolume() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class CMaximumVolume {
        public void solve(int testNumber, inputClass sc, PrintWriter out) {
            double L = sc.nextDouble();
            BigDecimal a = BigDecimal.valueOf(L / 3);
            out.println(a.multiply(a).multiply(a).toPlainString());
        }

    } CMaximumVolume public void solve(int testNumber, inputClass sc, PrintWriter out) {
            double L = sc.nextDouble();
            BigDecimal a = BigDecimal.valueOf(L / 3);
            out.println(a.multiply(a).multiply(a).toPlainString());
        } solve {
            double L = sc.nextDouble();
            BigDecimal a = BigDecimal.valueOf(L / 3);
            out.println(a.multiply(a).multiply(a).toPlainString());
        } double L = sc.nextDouble(); L sc.nextDouble() sc.nextDouble sc BigDecimal a = BigDecimal.valueOf(L / 3); a BigDecimal.valueOf(L / 3) BigDecimal.valueOf BigDecimal L / 3 L 3 out.println(a.multiply(a).multiply(a).toPlainString()) out.println out a.multiply(a).multiply(a).toPlainString() a.multiply(a).multiply(a).toPlainString a.multiply(a).multiply(a) a.multiply(a).multiply a.multiply(a) a.multiply a a a int testNumber testNumber inputClass sc sc PrintWriter out out static class inputClass {
        BufferedReader br;
        StringTokenizer st;

        public inputClass(InputStream in) {

            br = new BufferedReader(new InputStreamReader(in));
        }

        public String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }

    } inputClass BufferedReader br; br StringTokenizer st; st public inputClass(InputStream in) {

            br = new BufferedReader(new InputStreamReader(in));
        } inputClass {

            br = new BufferedReader(new InputStreamReader(in));
        } br = new BufferedReader(new InputStreamReader(in)) br new BufferedReader(new InputStreamReader(in)) InputStream in in public String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        } next {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        } while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } st == null || !st.hasMoreElements() st == null st null !st.hasMoreElements() st.hasMoreElements() st.hasMoreElements st {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } IOException e {
                    e.printStackTrace();
                } e.printStackTrace() e.printStackTrace e {
                    st = new StringTokenizer(br.readLine());
                } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st public double nextDouble() {
            return Double.parseDouble(next());
        } nextDouble {
            return Double.parseDouble(next());
        } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        inputClass in = new inputClass(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        CMaximumVolume solver = new CMaximumVolume();
        solver.solve(1, in, out);
        out.close();
    }

    static class CMaximumVolume {
        public void solve(int testNumber, inputClass sc, PrintWriter out) {
            double L = sc.nextDouble();
            BigDecimal a = BigDecimal.valueOf(L / 3);
            out.println(a.multiply(a).multiply(a).toPlainString());
        }

    }

    static class inputClass {
        BufferedReader br;
        StringTokenizer st;

        public inputClass(InputStream in) {

            br = new BufferedReader(new InputStreamReader(in));
        }

        public String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }

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

    static class CMaximumVolume {
        public void solve(int testNumber, inputClass sc, PrintWriter out) {
            double L = sc.nextDouble();
            BigDecimal a = BigDecimal.valueOf(L / 3);
            out.println(a.multiply(a).multiply(a).toPlainString());
        }

    }

    static class inputClass {
        BufferedReader br;
        StringTokenizer st;

        public inputClass(InputStream in) {

            br = new BufferedReader(new InputStreamReader(in));
        }

        public String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }

    }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

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

    static class CMaximumVolume {
        public void solve(int testNumber, inputClass sc, PrintWriter out) {
            double L = sc.nextDouble();
            BigDecimal a = BigDecimal.valueOf(L / 3);
            out.println(a.multiply(a).multiply(a).toPlainString());
        }

    }

    static class inputClass {
        BufferedReader br;
        StringTokenizer st;

        public inputClass(InputStream in) {

            br = new BufferedReader(new InputStreamReader(in));
        }

        public String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }

    }
}

