n Before entering their CS, each Pi receives a number. Holder of smallest number enter CS (like in bakeries, ice-cream stores...) n When Pi and Pj receives same number: u if i<j then Pi is served first, else Pj is served first n Pi resets its number to 0 in the exit section n Notation: u (a,b) < (c,d) if a < c or if a = c and b < d u max(a0,...ak) is a number b such that F b >= ai for i=0,..k