empty string can not get -1, you can use return "" if s =="" in front of other code.

Aha, I see :-) Thank you very much again! This really helps!

your code failed at s="" ;-)

You can paste your code here, let me see ;-)
(please Mark it as having spoiler content)

Could your exercise possibly at least show what input causes user's code to crash?

I am not really sure how difficult would it be but for I beginner as myself it would be really appreciated :)
Frankly, my code passes the basic tests but I am getting same error as cbira353.

perhaps your code sometimes generate some invalid index, such as -1, null..

You should return the answer, not print it.

In most of the languages, it should be lowercase true, but in at least Python, it should be the capitalized True. Unfortunately, we can't have a different description per language. Any suggestions for how to handle this discrepancy?

This is an error and unfortunatly cannot be resolved because 500+ solutions have been submitted..