//パターン1：OK(小数点以下切り捨て)
import java.math.BigDecimal;
import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();

		BigDecimal wSide = new BigDecimal((double)len/3);
		BigDecimal tSide = new BigDecimal((double)len/3);
		BigDecimal hSide = new BigDecimal((double)len/3);

//		System.out.println(wSide);
//		System.out.println(tSide);
//		System.out.println(hSide);

		BigDecimal result = wSide.multiply(tSide).multiply(hSide);

		System.out.print(result);
		sc.close();
	}
}


//パターン2：OK(小数点以下6桁以降に桁落ちアリ)
//package ojt.AtCoder;
//import java.util.Scanner;
//public class TestC_159 {
//	public static void main(String[] args) {
//		Scanner sc = new Scanner(System.in);
//		int len = sc.nextInt();
//
//		double wSide = (double)len/3;
//		double tSide = (double)len/3;
//		double hSide = (double)len/3;
//
//		System.out.println(wSide);
//		System.out.println(tSide);
//		System.out.println(hSide);
//
//		double result = wSide*tSide*hSide;
//
//		System.out.print(result);
//		sc.close();
//	}
//}


//パターン3：OK(小数点以下6桁以降に桁落ちアリ)
//package ojt.AtCoder;
//import java.util.Scanner;
//public class TestC_159 {
//	public static void main(String[] args) {
//		Scanner sc = new Scanner(System.in);
//		double len = sc.nextDouble();
//
//		System.out.println(Math.pow(len/3 , 3));
//
//		sc.close();
//	}
//} import java.math.BigDecimal; BigDecimal java.math import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();

		BigDecimal wSide = new BigDecimal((double)len/3);
		BigDecimal tSide = new BigDecimal((double)len/3);
		BigDecimal hSide = new BigDecimal((double)len/3);

//		System.out.println(wSide);
//		System.out.println(tSide);
//		System.out.println(hSide);

		BigDecimal result = wSide.multiply(tSide).multiply(hSide);

		System.out.print(result);
		sc.close();
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();

		BigDecimal wSide = new BigDecimal((double)len/3);
		BigDecimal tSide = new BigDecimal((double)len/3);
		BigDecimal hSide = new BigDecimal((double)len/3);

//		System.out.println(wSide);
//		System.out.println(tSide);
//		System.out.println(hSide);

		BigDecimal result = wSide.multiply(tSide).multiply(hSide);

		System.out.print(result);
		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();

		BigDecimal wSide = new BigDecimal((double)len/3);
		BigDecimal tSide = new BigDecimal((double)len/3);
		BigDecimal hSide = new BigDecimal((double)len/3);

//		System.out.println(wSide);
//		System.out.println(tSide);
//		System.out.println(hSide);

		BigDecimal result = wSide.multiply(tSide).multiply(hSide);

		System.out.print(result);
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int len = sc.nextInt(); len sc.nextInt() sc.nextInt sc BigDecimal wSide = new BigDecimal((double)len/3); wSide new BigDecimal((double)len/3) BigDecimal tSide = new BigDecimal((double)len/3); tSide new BigDecimal((double)len/3) BigDecimal hSide = new BigDecimal((double)len/3); hSide new BigDecimal((double)len/3) BigDecimal result = wSide.multiply(tSide).multiply(hSide); result wSide.multiply(tSide).multiply(hSide) wSide.multiply(tSide).multiply wSide.multiply(tSide) wSide.multiply wSide tSide hSide System.out.print(result) System.out.print System.out System System.out result sc.close() sc.close sc String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();

		BigDecimal wSide = new BigDecimal((double)len/3);
		BigDecimal tSide = new BigDecimal((double)len/3);
		BigDecimal hSide = new BigDecimal((double)len/3);

//		System.out.println(wSide);
//		System.out.println(tSide);
//		System.out.println(hSide);

		BigDecimal result = wSide.multiply(tSide).multiply(hSide);

		System.out.print(result);
		sc.close();
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();

		BigDecimal wSide = new BigDecimal((double)len/3);
		BigDecimal tSide = new BigDecimal((double)len/3);
		BigDecimal hSide = new BigDecimal((double)len/3);

//		System.out.println(wSide);
//		System.out.println(tSide);
//		System.out.println(hSide);

		BigDecimal result = wSide.multiply(tSide).multiply(hSide);

		System.out.print(result);
		sc.close();
	}
} Main
//パターン1：OK(小数点以下切り捨て)
import java.math.BigDecimal;
import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();

		BigDecimal wSide = new BigDecimal((double)len/3);
		BigDecimal tSide = new BigDecimal((double)len/3);
		BigDecimal hSide = new BigDecimal((double)len/3);

//		System.out.println(wSide);
//		System.out.println(tSide);
//		System.out.println(hSide);

		BigDecimal result = wSide.multiply(tSide).multiply(hSide);

		System.out.print(result);
		sc.close();
	}
}


//パターン2：OK(小数点以下6桁以降に桁落ちアリ)
//package ojt.AtCoder;
//import java.util.Scanner;
//public class TestC_159 {
//	public static void main(String[] args) {
//		Scanner sc = new Scanner(System.in);
//		int len = sc.nextInt();
//
//		double wSide = (double)len/3;
//		double tSide = (double)len/3;
//		double hSide = (double)len/3;
//
//		System.out.println(wSide);
//		System.out.println(tSide);
//		System.out.println(hSide);
//
//		double result = wSide*tSide*hSide;
//
//		System.out.print(result);
//		sc.close();
//	}
//}


//パターン3：OK(小数点以下6桁以降に桁落ちアリ)
//package ojt.AtCoder;
//import java.util.Scanner;
//public class TestC_159 {
//	public static void main(String[] args) {
//		Scanner sc = new Scanner(System.in);
//		double len = sc.nextDouble();
//
//		System.out.println(Math.pow(len/3 , 3));
//
//		sc.close();
//	}
//}
