(* THEN (OK): *)

Lemma not_between_B0:forall(m:fmap)(x z:dart),
inv_hmap m -> exd m x -> exd m z -> x <> z ->
let z0:= bottom m zero z in
~betweene m z0 x z ->
(~MA0.expo m z0 x
\/  forall(i j:nat),
x = Iter (MA0.f m) i z0 ->
z = Iter (MA0.f m) j z0 ->
(i < MA0.Iter_upb m z0)%nat ->
(j < MA0.Iter_upb m z0)%nat ->
(j <= i)%nat).