OP solved it, closing. Also description has been updated

It is not considered a range unless it spans at least 3 numbers. For example "12,13,15-17"

So, your example above should return -54,-53 and -68--66 respectively.

Bringing accuracy to:

Simple random tests (10 of 10 statements)
Medium random tests (18 of 20 statements)
Hard random tests (100 of 100 statements)

Can't figure out what's wrong.
What a challenge!!!

May be i choosed strange way to solve this task: iterate from first day to last day, remove values less than day from input array. But i can't pass medium tests and 2nd basic third REALTIME day in a row :) Yep...I red how to round in description and comments, but still can't understand how to do it correct...I'm using math.ceil()

2nd basic test. 10nd day
62.00000000000001 rounding to 63. But in correct result 62...why???

well some years ago you couldnt even print "hello world". I mean, your skill is growing so dont be upset. I believe you'll be able to solve this kata soon

sorry i found this page, but was thinking that ` = ' ...

Please use markdown tags to format your code or it's unusable, see there: https://docs.codewars.com/training/troubleshooting/#post-discourse

Negative values in this kata might look strange after formatting, but they don't really need any special handling. You process negative values exactly the same way as positive ones.
You can show your code so maybe we could find your problem and help you.

Please explain me somebody how to deal with values like -54--53 or -68--66 in input list? I'm trying convert it to str in cycle, but it gives me result: -1 or -2. I don't see other method to put it in returning string. Or should i just see solutions because i'm tottaly in other way to deal with this kata?

can you explain me pls why is it happening?
btw at first i was trying use int(1/epsilon + 0.5). it's working different for couple examples and this i can't understand too, because it should round number to bigger like math.ceil, isn't it?

Please only mark issue for kata issues.

arr[len(arr)] is out of range since indexing starts at 0.

Also, you can use markdown to format your code.