import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        double l;
        double n,m;
        
        l = sc.nextInt();
        
        n = l / 3;
        
        m = l - n - n;
        
        System.out.println(n * n * m);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        double l;
        double n,m;
        
        l = sc.nextInt();
        
        n = l / 3;
        
        m = l - n - n;
        
        System.out.println(n * n * m);
    }
} Main public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        double l;
        double n,m;
        
        l = sc.nextInt();
        
        n = l / 3;
        
        m = l - n - n;
        
        System.out.println(n * n * m);
    } main {
        
        Scanner sc = new Scanner(System.in);
        double l;
        double n,m;
        
        l = sc.nextInt();
        
        n = l / 3;
        
        m = l - n - n;
        
        System.out.println(n * n * m);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) double l; l double n n m; m l = sc.nextInt() l sc.nextInt() sc.nextInt sc n = l / 3 n l / 3 l 3 m = l - n - n m l - n - n l - n - n l n n System.out.println(n * n * m) System.out.println System.out System System.out n * n * m n * n * m n n m String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        double l;
        double n,m;
        
        l = sc.nextInt();
        
        n = l / 3;
        
        m = l - n - n;
        
        System.out.println(n * n * m);
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        double l;
        double n,m;
        
        l = sc.nextInt();
        
        n = l / 3;
        
        m = l - n - n;
        
        System.out.println(n * n * m);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        double l;
        double n,m;
        
        l = sc.nextInt();
        
        n = l / 3;
        
        m = l - n - n;
        
        System.out.println(n * n * m);
    }
}
