You only need to iterate the array once to get your result. Observe and analyze how step can help in this regard.

oh! Thank you. lol I need more coffee

I know, but that's wrong, num is a number.

I'm trying to define i as the index of the number in each array and num[i+1] is the next number over.

Thanks for looking at this

Fix.

What is num[i+1]?

It was a problem with your code. Not a kata issue.

You're probably parsing the number and that fails because they're too big. Try another way.

Expected: '[9, 2, 2, 3, 3, 7, 2, 0, 3, 6, 8, 5, 4, 7, 7, 5, 8, 0, 8]', instead got: '[9, 2, 2, 3, 3, 7, 2, 0, 3, 6, 8, 5, 4, 7, 7, 6, 0, 0, 0]'
Expected: '[9, 2, 2, 3, 3, 7, 2, 0, 3, 6, 8, 5, 4, 7, 7, 5, 8, 0, 7, 5, 3, 2, 6, 7, 8, 4, 2, 4, 2, 6, 7, 8, 7, 4, 5, 2, 2]', instead got: '[9, NaN, 2, 2, 3, 3, 7, 2, 0, 3, 6, 8, 5, 4, 7, 7, 6, NaN, NaN, 3, 6]'

i'm passing all other test specs