import java.util.*;
import java.io.*;
public class Main {
    static Scanner sc = new Scanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    long mod = 998244353;
    long[] frac, inv;
    public static void main(String[] args){
        Main main = new Main();
//        String ans = main.solve()<0?"No":"Yes";
        System.out.println(main.solve());
    }
    double solve(){
        double l = sc.nextDouble();
        l = l/3.0;
        return l*l*l;
    }
} import java.util.*; util.* java import java.io.*; io.* java public class Main {
    static Scanner sc = new Scanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    long mod = 998244353;
    long[] frac, inv;
    public static void main(String[] args){
        Main main = new Main();
//        String ans = main.solve()<0?"No":"Yes";
        System.out.println(main.solve());
    }
    double solve(){
        double l = sc.nextDouble();
        l = l/3.0;
        return l*l*l;
    }
} Main static Scanner sc = new Scanner(System.in); sc new Scanner(System.in) static PrintWriter out = new PrintWriter(System.out); out new PrintWriter(System.out) static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); reader new BufferedReader(new InputStreamReader(System.in)) long mod = 998244353; mod 998244353 long[] frac frac inv; inv public static void main(String[] args){
        Main main = new Main();
//        String ans = main.solve()<0?"No":"Yes";
        System.out.println(main.solve());
    } main {
        Main main = new Main();
//        String ans = main.solve()<0?"No":"Yes";
        System.out.println(main.solve());
    } Main main = new Main(); main new Main() System.out.println(main.solve()) System.out.println System.out System System.out main.solve() main.solve main String[] args args double solve(){
        double l = sc.nextDouble();
        l = l/3.0;
        return l*l*l;
    } solve {
        double l = sc.nextDouble();
        l = l/3.0;
        return l*l*l;
    } double l = sc.nextDouble(); l sc.nextDouble() sc.nextDouble sc l = l/3.0 l l/3.0 l 3.0 return l*l*l; l*l*l l*l*l l l l public class Main {
    static Scanner sc = new Scanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    long mod = 998244353;
    long[] frac, inv;
    public static void main(String[] args){
        Main main = new Main();
//        String ans = main.solve()<0?"No":"Yes";
        System.out.println(main.solve());
    }
    double solve(){
        double l = sc.nextDouble();
        l = l/3.0;
        return l*l*l;
    }
} public class Main {
    static Scanner sc = new Scanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    long mod = 998244353;
    long[] frac, inv;
    public static void main(String[] args){
        Main main = new Main();
//        String ans = main.solve()<0?"No":"Yes";
        System.out.println(main.solve());
    }
    double solve(){
        double l = sc.nextDouble();
        l = l/3.0;
        return l*l*l;
    }
} Main
import java.util.*;
import java.io.*;
public class Main {
    static Scanner sc = new Scanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    long mod = 998244353;
    long[] frac, inv;
    public static void main(String[] args){
        Main main = new Main();
//        String ans = main.solve()<0?"No":"Yes";
        System.out.println(main.solve());
    }
    double solve(){
        double l = sc.nextDouble();
        l = l/3.0;
        return l*l*l;
    }
}
