Definition Q2(m:fmap)(z:dart)(s:set):Prop:=
exds s (Iter (f m) (ndN m - card s)%nat z) ->
(card (Iter_rem_aux m z s) < card s)%nat.

Lemma LQ2:forall(m:fmap)(z:dart)(s:set),
exds s (Iter (f m) (ndN m - card s) z) ->
(card (Iter_rem_aux m z s) < card s)%nat.