Cullen: One way to think about cohorts a is it's pretty simple. What you want to see is that your month zero and month one metrics are getting stronger overtime, so people are getting more engaged faster. You also want to see that towards the tail end of whatever you're tracking, in month five or month six, for example, your retention rate is is increasing overtime. And that generally will give you a good sense of is my product getting more healthy, and my connecting more value to the user, and my acquiring better customers, et cetera, etc.