Dr. Pepper-
“Feel free to use any method you want” releases me from your “no cheating” prohibition and associated assignment (you wouldn’t be able to read my chicken-scratch handwriting, anyway), so I Googled it.
I saw something about “log”, which rings a very faint unused-for-decades bell, but no “aha!” moment, unfortunately.
You may want to keep your puzzle open a little longer for other folks who want to try it, but at this point I’m giving up.