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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.
It seems I broke the rule from the problem statement, but I can't remember to have read that by the time I implemented my solution (it was 8 yeas ago, by the way).
This comment is hidden because it contains spoiler information about the solution
Well, your num_sym list logic is wrong. It contains the letter s and that's why it fails. Your code isn't shifting it.
demonstrate what can be done, be original, have fun.