import java.io.BufferedReader;
import java.io.*;
import java.util.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;
public class Main {
	public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);

    int l = sc.nextInt();

    if((double)l % 3.0 == 0.0){
        System.out.println((double)l*l*l/27);
    }else{
        System.out.println((double)l/3*(double)l/3*(double)l/3);
    }
    
    
    
    
	}
} import java.io.BufferedReader; BufferedReader java.io import java.io.*; io.* java import java.util.*; util.* java import java.util.ArrayList; ArrayList java.util import java.util.Iterator; Iterator java.util import java.util.List; List java.util import java.util.Collections; Collections java.util public class Main {
	public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);

    int l = sc.nextInt();

    if((double)l % 3.0 == 0.0){
        System.out.println((double)l*l*l/27);
    }else{
        System.out.println((double)l/3*(double)l/3*(double)l/3);
    }
    
    
    
    
	}
} Main public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);

    int l = sc.nextInt();

    if((double)l % 3.0 == 0.0){
        System.out.println((double)l*l*l/27);
    }else{
        System.out.println((double)l/3*(double)l/3*(double)l/3);
    }
    
    
    
    
	} main {
    
    Scanner sc = new Scanner(System.in);

    int l = sc.nextInt();

    if((double)l % 3.0 == 0.0){
        System.out.println((double)l*l*l/27);
    }else{
        System.out.println((double)l/3*(double)l/3*(double)l/3);
    }
    
    
    
    
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int l = sc.nextInt(); l sc.nextInt() sc.nextInt sc if((double)l % 3.0 == 0.0){
        System.out.println((double)l*l*l/27);
    }else{
        System.out.println((double)l/3*(double)l/3*(double)l/3);
    } (double)l % 3.0 == 0.0 (double)l % 3.0 (double)l 3.0 0.0 {
        System.out.println((double)l*l*l/27);
    } System.out.println((double)l*l*l/27) System.out.println System.out System System.out (double)l*l*l/27 (double)l*l*l (double)l*l*l (double)l l l 27 {
        System.out.println((double)l/3*(double)l/3*(double)l/3);
    } System.out.println((double)l/3*(double)l/3*(double)l/3) System.out.println System.out System System.out (double)l/3*(double)l/3*(double)l/3 (double)l/3*(double)l/3*(double)l (double)l/3*(double)l/3 (double)l/3*(double)l (double)l/3 (double)l 3 (double)l 3 (double)l 3 final String[] args args public class Main {
	public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);

    int l = sc.nextInt();

    if((double)l % 3.0 == 0.0){
        System.out.println((double)l*l*l/27);
    }else{
        System.out.println((double)l/3*(double)l/3*(double)l/3);
    }
    
    
    
    
	}
} public class Main {
	public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);

    int l = sc.nextInt();

    if((double)l % 3.0 == 0.0){
        System.out.println((double)l*l*l/27);
    }else{
        System.out.println((double)l/3*(double)l/3*(double)l/3);
    }
    
    
    
    
	}
} Main
import java.io.BufferedReader;
import java.io.*;
import java.util.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;
public class Main {
	public static void main(final String[] args){
    
    Scanner sc = new Scanner(System.in);

    int l = sc.nextInt();

    if((double)l % 3.0 == 0.0){
        System.out.println((double)l*l*l/27);
    }else{
        System.out.println((double)l/3*(double)l/3*(double)l/3);
    }
    
    
    
    
	}
}