@joe_padon I think you make a good point - there are TONS of extensions for this task! Depending on who your students are, I think you could even get into a discussion about run time. I think this goes WAY beyond the intent of the lesson, but having extensions ready to go is always important!
Another thing to watch out for is students taking a little creative liberty with the code. My students finished really fast too, but then I realized they were using if, then statements and while loops (neither of which are "approved" lines of code). Once I realized this I made them go back and figure it out again... that took them a bit more time.