import java.util.Scanner;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner sc = new Scanner(System.in);
		
		float value = sc.nextFloat();
		
		
		float max = value/3;
		
		float result = max*max*max;
		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