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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.
So when in the first if statement it checks to see they are both numbers and to therefore return 0 it would stop for example a user being able to input any letter. So checking a and b are both numbers first prevents that bug. I hope Im explaining it right