there is z2 given x2 before that there was x2 given x1 then with that there was right before that Z 1 given x1 and then before that there was x1 given x0 and before that there was z 0 given x0 and then distribution for X 0 and the graph corresponding to this is X 0 as to capitals x0 x1 x2 and then observed Z 0 C 1 Z 2 so we just throw it out the fool joint over all six variables here but then we only care about these four so we sum out over X 0 and X 1 to get distribution over just a 4 we care about now what do we do in