(* OK: INDUCTION ON i!*)

Lemma expf_L0_CN_2:forall (m:fmap)(x y z:dart)(i:nat),
inv_hmap (L m zero x y) -> exd m z ->
let x0 := cA m zero x in
let x_1 := cA_1 m one x in
let y_0:= cA_1 m zero y in
let y_0_1 := cA_1 m one y_0 in
let t:= Iter (cF (L m zero x y)) i z in
~expf m x_1 y ->
(expf m z t
\/ expf m z y /\ expf m t x0
\/ expf m t y /\ expf m z x0).