Or you just do the math to compute this formula.

Hello benlynch,

Only got to know of your comment today! 28 days later...

Thanks!

You can check the tags of a kata before trying it. The ones tagged "Puzzles" often require some guessing and trial and error. Not everyone likes these kinds of challenges, so it's ok if you want to avoid them.

Please don't give hints in the comments of puzzle challenges.

Thank you for the feedback. Glad you enjoyed the solution and got something out of it.