Definition R2
(m:fmap)(z:dart)(s:set):Prop:=
let sr := Iter_rem_aux m z s in
~ exds sr (Iter (f m) (ndN m - card s)%nat z).

(* Specifications: *)
Lemma LR2 :
forall(m:fmap)(z:dart)(s:set),
let sr := Iter_rem_aux m z s in
~ exds sr (Iter (f m) (ndN m - card s)%nat z).