import java.util.*;
import java.io.*;
public class Main {
    public static void main(String[] args) throws IOException{
    	// Solution sol = new Solution();
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	StringTokenizer st = new StringTokenizer(br.readLine());
    	int N = Integer.parseInt(st.nextToken());
    	double k = (double)N/3;
    	System.out.println(Math.pow(k,3));

    }
} import java.util.*; util.* java import java.io.*; io.* java public class Main {
    public static void main(String[] args) throws IOException{
    	// Solution sol = new Solution();
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	StringTokenizer st = new StringTokenizer(br.readLine());
    	int N = Integer.parseInt(st.nextToken());
    	double k = (double)N/3;
    	System.out.println(Math.pow(k,3));

    }
} Main public static void main(String[] args) throws IOException{
    	// Solution sol = new Solution();
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	StringTokenizer st = new StringTokenizer(br.readLine());
    	int N = Integer.parseInt(st.nextToken());
    	double k = (double)N/3;
    	System.out.println(Math.pow(k,3));

    } main {
    	// Solution sol = new Solution();
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	StringTokenizer st = new StringTokenizer(br.readLine());
    	int N = Integer.parseInt(st.nextToken());
    	double k = (double)N/3;
    	System.out.println(Math.pow(k,3));

    } BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); br new BufferedReader(new InputStreamReader(System.in)) StringTokenizer st = new StringTokenizer(br.readLine()); st new StringTokenizer(br.readLine()) int N = Integer.parseInt(st.nextToken()); N Integer.parseInt(st.nextToken()) Integer.parseInt Integer st.nextToken() st.nextToken st double k = (double)N/3; k (double)N/3 (double)N 3 System.out.println(Math.pow(k,3)) System.out.println System.out System System.out Math.pow(k,3) Math.pow Math k 3 String[] args args public class Main {
    public static void main(String[] args) throws IOException{
    	// Solution sol = new Solution();
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	StringTokenizer st = new StringTokenizer(br.readLine());
    	int N = Integer.parseInt(st.nextToken());
    	double k = (double)N/3;
    	System.out.println(Math.pow(k,3));

    }
} public class Main {
    public static void main(String[] args) throws IOException{
    	// Solution sol = new Solution();
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	StringTokenizer st = new StringTokenizer(br.readLine());
    	int N = Integer.parseInt(st.nextToken());
    	double k = (double)N/3;
    	System.out.println(Math.pow(k,3));

    }
} Main
import java.util.*;
import java.io.*;
public class Main {
    public static void main(String[] args) throws IOException{
    	// Solution sol = new Solution();
    	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	StringTokenizer st = new StringTokenizer(br.readLine());
    	int N = Integer.parseInt(st.nextToken());
    	double k = (double)N/3;
    	System.out.println(Math.pow(k,3));

    }
}