specific case you get the common smoother so you find that the math for common smoother is very similar to come on filter which agnostic covered will be very similar equations happening that are really just matrix updates you don't need to do any explicit integration any kind of weird integrals that are hard to compute no these closed forms you just manipulate matrices and you'll find updates for your covariance matrix and for your mean and this case will come from both sides and then I'll come together and give you the smooth