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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 description does not specify what the expected output for a missing input is so you don't have to account for this case. If it would still be tested then this would be worth a kata issue but
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inputs just don't make sense for this kata.