Loading collection data...
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.
Why? Because you're returning incorrect results? You should always be returning single digit numbers, read the description again if it's not clear.
You're returning 15 and expected is 6.