(* OK: ALL z^i FOR n0 <=i <= nr-1 EXIST IN s: *)
Definition P6(m:fmap)(z:dart)(s:set):Prop:=
inv_hmap m ->
(card s <= ndN m ->
let n0:= ndN m - card s in
let nr:= Iter_upb_aux m z s in
exds s (Iter (f m) n0 z) ->
exds_int m z n0 (nr - 1) s)%nat.
(* OK: LONG... *)

Lemma LP6:forall(m:fmap)(z:dart)(s:set),
inv_hmap m ->
(card s <= ndN m ->
let n0:= ndN m - card s in
let nr:= Iter_upb_aux m z s in
exds s (Iter (f m) n0 z) ->
exds_int m z n0 (nr - 1) s)%nat.