init {
	stock := nil
	shortage := nil
}

channel CIO_enter {
	out deriver(s:Tuple, arrive(item:Str, num:Int)) = tuple(item, num, num)
}

channel C3 {
	in deriver(dr, update3(dr2)) = dr2
	out shipping(sp:Tuple, update3(dr2)) = tuple(fst(dr2), fst(snd(dr2)))
}