and see if I could re-derive it from scratch starting from a blank piece of paper as only if I could do that, and I would you know feel like yep, I think I understand this piece of math. And it turns out if you want to do this type of math yourself is your ability to derive this type of math, re-derive this type of math, that gives you the ability to generalize, to derive new novel pieces of math yourself. So I think I actually learned a lot of math, for several machine learning by doing this. And just by re-deriving other people's work that