Lemma Iter_cF_L1_i: forall(m:fmap)(x y z:dart)(i:nat), let m1:= L m one x y in let y0:= cA m zero y in inv_hmap m1 -> exd m z -> ~expf m x y0 -> ~expf m x z -> ~expf m y0 z -> Iter (cF m1) i z = Iter (cF m) i z.