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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.
should not with 900&400&90&40....so i think it not a good answer
In fact I even can't understand what it want us to do;
when input a number ,it doesn't work..............
regex is a fantastic job