import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		Scanner cin = new Scanner(System.in);
		
		Double L = cin.nextDouble();
		
		Double w = L/3;
		
		Double ans = w*(w-L)*(w-L)/4;
		
		System.out.println(ans);
		
	}

} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		Scanner cin = new Scanner(System.in);
		
		Double L = cin.nextDouble();
		
		Double w = L/3;
		
		Double ans = w*(w-L)*(w-L)/4;
		
		System.out.println(ans);
		
	}

} Main public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		Scanner cin = new Scanner(System.in);
		
		Double L = cin.nextDouble();
		
		Double w = L/3;
		
		Double ans = w*(w-L)*(w-L)/4;
		
		System.out.println(ans);
		
	} main {
		// TODO Auto-generated method stub
		
		Scanner cin = new Scanner(System.in);
		
		Double L = cin.nextDouble();
		
		Double w = L/3;
		
		Double ans = w*(w-L)*(w-L)/4;
		
		System.out.println(ans);
		
	} Scanner cin = new Scanner(System.in); cin new Scanner(System.in) Double L = cin.nextDouble(); L cin.nextDouble() cin.nextDouble cin Double w = L/3; w L/3 L 3 Double ans = w*(w-L)*(w-L)/4; ans w*(w-L)*(w-L)/4 w*(w-L)*(w-L) w*(w-L)*(w-L) w (w-L) w L (w-L) w L 4 System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		Scanner cin = new Scanner(System.in);
		
		Double L = cin.nextDouble();
		
		Double w = L/3;
		
		Double ans = w*(w-L)*(w-L)/4;
		
		System.out.println(ans);
		
	}

} public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		Scanner cin = new Scanner(System.in);
		
		Double L = cin.nextDouble();
		
		Double w = L/3;
		
		Double ans = w*(w-L)*(w-L)/4;
		
		System.out.println(ans);
		
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		Scanner cin = new Scanner(System.in);
		
		Double L = cin.nextDouble();
		
		Double w = L/3;
		
		Double ans = w*(w-L)*(w-L)/4;
		
		System.out.println(ans);
		
	}

}
