

import java.math.BigDecimal;
import java.util.Scanner;

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

		Scanner scan = new Scanner(System.in);

		int l = scan.nextInt();
		BigDecimal bigL = new BigDecimal(l * l * l);
		BigDecimal big27 = new BigDecimal(27.000000);

		BigDecimal result = bigL.divide(big27, 6, BigDecimal.ROUND_HALF_UP);

		System.out.println(result);
	}

}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz