Hi @eiphorie - in random tests, the value of n goes up to 10**19 or so meaning that actually creating the string is impossible, let alone counting inside it.

You have to find a smarter way to get the answer - for this, you can use your solution for smaller values of n to maybe try to find some patterns or help you debug.

This is actually more of a mathematics/logic type kata, so if you don't get the answer straight away then practicing on other katas will definitely improve your ability to "see" the correct approach and techniques. Hope that helps a bit