import java.util.*;
import java.math.BigDecimal;

public class Main {
    public static void main(final String[] args) {
        final Scanner sc = new Scanner(System.in);

        final int L = sc.nextInt();
        sc.close();
        double syo = L / 3.0;
        double amari = L - syo * 3.0;
        double V;
        if(amari > 0)
            V = syo * syo * (syo + amari);
        else
            V = syo * syo * syo;

        System.out.println(BigDecimal.valueOf(V).toPlainString());
    }
} import java.util.*; util.* java import java.math.BigDecimal; BigDecimal java.math public class Main {
    public static void main(final String[] args) {
        final Scanner sc = new Scanner(System.in);

        final int L = sc.nextInt();
        sc.close();
        double syo = L / 3.0;
        double amari = L - syo * 3.0;
        double V;
        if(amari > 0)
            V = syo * syo * (syo + amari);
        else
            V = syo * syo * syo;

        System.out.println(BigDecimal.valueOf(V).toPlainString());
    }
} Main public static void main(final String[] args) {
        final Scanner sc = new Scanner(System.in);

        final int L = sc.nextInt();
        sc.close();
        double syo = L / 3.0;
        double amari = L - syo * 3.0;
        double V;
        if(amari > 0)
            V = syo * syo * (syo + amari);
        else
            V = syo * syo * syo;

        System.out.println(BigDecimal.valueOf(V).toPlainString());
    } main {
        final Scanner sc = new Scanner(System.in);

        final int L = sc.nextInt();
        sc.close();
        double syo = L / 3.0;
        double amari = L - syo * 3.0;
        double V;
        if(amari > 0)
            V = syo * syo * (syo + amari);
        else
            V = syo * syo * syo;

        System.out.println(BigDecimal.valueOf(V).toPlainString());
    } final Scanner sc = new Scanner(System.in); sc new Scanner(System.in) final int L = sc.nextInt(); L sc.nextInt() sc.nextInt sc sc.close() sc.close sc double syo = L / 3.0; syo L / 3.0 L 3.0 double amari = L - syo * 3.0; amari L - syo * 3.0 L syo * 3.0 syo 3.0 double V; V if(amari > 0)
            V = syo * syo * (syo + amari);
        else
            V = syo * syo * syo; amari > 0 amari 0 V = syo * syo * (syo + amari) V syo * syo * (syo + amari) syo * syo * (syo + amari) syo syo (syo + amari) syo amari V = syo * syo * syo V syo * syo * syo syo * syo * syo syo syo syo System.out.println(BigDecimal.valueOf(V).toPlainString()) System.out.println System.out System System.out BigDecimal.valueOf(V).toPlainString() BigDecimal.valueOf(V).toPlainString BigDecimal.valueOf(V) BigDecimal.valueOf BigDecimal V final String[] args args public class Main {
    public static void main(final String[] args) {
        final Scanner sc = new Scanner(System.in);

        final int L = sc.nextInt();
        sc.close();
        double syo = L / 3.0;
        double amari = L - syo * 3.0;
        double V;
        if(amari > 0)
            V = syo * syo * (syo + amari);
        else
            V = syo * syo * syo;

        System.out.println(BigDecimal.valueOf(V).toPlainString());
    }
} public class Main {
    public static void main(final String[] args) {
        final Scanner sc = new Scanner(System.in);

        final int L = sc.nextInt();
        sc.close();
        double syo = L / 3.0;
        double amari = L - syo * 3.0;
        double V;
        if(amari > 0)
            V = syo * syo * (syo + amari);
        else
            V = syo * syo * syo;

        System.out.println(BigDecimal.valueOf(V).toPlainString());
    }
} Main
import java.util.*;
import java.math.BigDecimal;

public class Main {
    public static void main(final String[] args) {
        final Scanner sc = new Scanner(System.in);

        final int L = sc.nextInt();
        sc.close();
        double syo = L / 3.0;
        double amari = L - syo * 3.0;
        double V;
        if(amari > 0)
            V = syo * syo * (syo + amari);
        else
            V = syo * syo * syo;

        System.out.println(BigDecimal.valueOf(V).toPlainString());
    }
}