(* OK: *)

Lemma expf_L1_II_CNA_aux:forall (m:fmap)(x y z:dart)(i:nat),
let m1 := (L m one x y) in
let y0 := cA m zero y in
let m1 := (L m one x y) in
let t := Iter (cF m1) i z in
inv_hmap m1 -> exd m z ->
expf m x y0 -> ~ expf m x z ->
expf (L m one x y) z t ->
expf m z t.