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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
The timeout issues you've experienced are because your algorithm is slow (most solutions finish in <= 1sec), otherwise yes I agree that the description could be more explicit about the desired shape of the cartesian products.
Make a Python version, begging u :(