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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.
I have found the math formula for this problem and tested in local.Though I reduced the time complexity to O(n), It still show time out (12000 ms).It's a bit annoying。