
import java.util.Scanner;


public class Main 
{ 
    public static void main(String[] args) 
    {
        Scanner sc = new Scanner(System.in);
        float n = sc.nextInt();
        float dim = n/3;
        System.out.printf("%f\n",dim*dim*dim);
    }
}

/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