Still true, I could only pass by adding an extra "M" for every digit higher in thousands place. Otherwise 6 cases failed consistently.

This one was tough, took me hours! It sounded like it would be much simpler, but in practice, I had to rethink my approach several times and more or less start over.All the while my brain kept maxing out its working memory. Pretty good!

I was looking at your code after I finally gave up on the kata(couldnt make it past n=1400 before timeout).
I was breaking down how you did it. I was puzzled for a bit over where it iterated through the numbers until it got to n. Then I realized the format of the test asks them in sequential order. You clearly are advanced enough to easily implement the loop but you knew,to pass the test, you didnt have to. I consider that clever!