import java.math.*;
import java.util.*;

	public class Main {

		public static void main(String[] args) {

			Scanner sc = new Scanner(System.in);
			int L = sc.nextInt();
			double a= L/3.0;
			double b= L/3.0;
			double v = a*b*(L-a-b);
			
			System.out.println(v);
			
		}

	} import java.math.*; math.* java import java.util.*; util.* java public class Main {

		public static void main(String[] args) {

			Scanner sc = new Scanner(System.in);
			int L = sc.nextInt();
			double a= L/3.0;
			double b= L/3.0;
			double v = a*b*(L-a-b);
			
			System.out.println(v);
			
		}

	} Main public static void main(String[] args) {

			Scanner sc = new Scanner(System.in);
			int L = sc.nextInt();
			double a= L/3.0;
			double b= L/3.0;
			double v = a*b*(L-a-b);
			
			System.out.println(v);
			
		} main {

			Scanner sc = new Scanner(System.in);
			int L = sc.nextInt();
			double a= L/3.0;
			double b= L/3.0;
			double v = a*b*(L-a-b);
			
			System.out.println(v);
			
		} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int L = sc.nextInt(); L sc.nextInt() sc.nextInt sc double a= L/3.0; a L/3.0 L 3.0 double b= L/3.0; b L/3.0 L 3.0 double v = a*b*(L-a-b); v a*b*(L-a-b) a*b*(L-a-b) a b (L-a-b) L-a-b L a b System.out.println(v) System.out.println System.out System System.out v String[] args args public class Main {

		public static void main(String[] args) {

			Scanner sc = new Scanner(System.in);
			int L = sc.nextInt();
			double a= L/3.0;
			double b= L/3.0;
			double v = a*b*(L-a-b);
			
			System.out.println(v);
			
		}

	} public class Main {

		public static void main(String[] args) {

			Scanner sc = new Scanner(System.in);
			int L = sc.nextInt();
			double a= L/3.0;
			double b= L/3.0;
			double v = a*b*(L-a-b);
			
			System.out.println(v);
			
		}

	} Main
import java.math.*;
import java.util.*;

	public class Main {

		public static void main(String[] args) {

			Scanner sc = new Scanner(System.in);
			int L = sc.nextInt();
			double a= L/3.0;
			double b= L/3.0;
			double v = a*b*(L-a-b);
			
			System.out.println(v);
			
		}

	}