right spots you reduces and you get a linear competition in the length of the network rather than an exponential calculation so can we do the same thing here well let's see how about X 0 actually we can play the same trick as before X 0 instead of summing over it over here where does it appear only in the back here so let's just insert that summation over here how about X 1 all of these are constants as far as X 1 is concerned so we can put the summation over X 1 over here and get rid of it over here then as we think of this thing here so we