that if you then run bits back coding using these two distributions so this was Z given X here Q this P of X given Z so if you run Kota using these two distributions the code link that you get from bits fat coding will be exactly what we wanted plus this little error term which is this second-order error term so so that this is how you turn or this is a way of turning a flu model into a compression algorithm is to convert it into is to locally approximate it with a certain beauty to find like this and then the