Hello - I was experimenting with using a subset of string handling, to see if I could get the algorithm working. But you are correct - there are much better (quicker) ways of getting the same effect with built-in functions! Thanks, and stay safe! :-)

yeah, we could have write list as string and avoid int parse thing but nvm

You are asked how many number in range from a to b (both inclusive) do not have digit 5. For example:

2, 69, 301, 280013 - good
(5), (5)6, 2(5)0, 12321(5) - bad