import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    }
    
	//フィールド
    Scanner sc;
    double L;
    
    //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.L = sc.nextDouble();
    }
    
    //解答処理
    private double solve() {
        double volume = Math.pow(L/3, 3);
        return volume;
    }
    
    //出力
    public void show(double answer) {
        System.out.printf("%.12f",answer);
    }

} import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    }
    
	//フィールド
    Scanner sc;
    double L;
    
    //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.L = sc.nextDouble();
    }
    
    //解答処理
    private double solve() {
        double volume = Math.pow(L/3, 3);
        return volume;
    }
    
    //出力
    public void show(double answer) {
        System.out.printf("%.12f",answer);
    }

} Main //フィールド
    Scanner sc; sc double L; L public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) Main m = new Main(sc); m new Main(sc) m.show(m.solve()) m.show m m.solve() m.solve m sc.close() sc.close sc String[] args args //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.L = sc.nextDouble();
    } Main {
        this.sc = sc;
        this.L = sc.nextDouble();
    } this.sc = sc this.sc this this.sc sc this.L = sc.nextDouble() this.L this this.L sc.nextDouble() sc.nextDouble sc Scanner sc sc //解答処理
    private double solve() {
        double volume = Math.pow(L/3, 3);
        return volume;
    } solve {
        double volume = Math.pow(L/3, 3);
        return volume;
    } double volume = Math.pow(L/3, 3); volume Math.pow(L/3, 3) Math.pow Math L/3 L 3 3 return volume; volume //出力
    public void show(double answer) {
        System.out.printf("%.12f",answer);
    } show {
        System.out.printf("%.12f",answer);
    } System.out.printf("%.12f",answer) System.out.printf System.out System System.out "%.12f" answer double answer answer public class Main {
	public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    }
    
	//フィールド
    Scanner sc;
    double L;
    
    //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.L = sc.nextDouble();
    }
    
    //解答処理
    private double solve() {
        double volume = Math.pow(L/3, 3);
        return volume;
    }
    
    //出力
    public void show(double answer) {
        System.out.printf("%.12f",answer);
    }

} public class Main {
	public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    }
    
	//フィールド
    Scanner sc;
    double L;
    
    //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.L = sc.nextDouble();
    }
    
    //解答処理
    private double solve() {
        double volume = Math.pow(L/3, 3);
        return volume;
    }
    
    //出力
    public void show(double answer) {
        System.out.printf("%.12f",answer);
    }

} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        Main m = new Main(sc);
        m.show(m.solve());
        sc.close();
    }
    
	//フィールド
    Scanner sc;
    double L;
    
    //入力
    Main(Scanner sc) {
        this.sc = sc;
        this.L = sc.nextDouble();
    }
    
    //解答処理
    private double solve() {
        double volume = Math.pow(L/3, 3);
        return volume;
    }
    
    //出力
    public void show(double answer) {
        System.out.printf("%.12f",answer);
    }

}