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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.
Use spoiler flag.
It's also testing backwards.
Your input is
[3]. Allowed return values would be12,21or30.Because there can be multiple possibilities, the test checks the resulting sums of digits, not the return value itself. Those digit sums are unique.