Inductive plus: state -> state -> Prop :=
| plus_left: forall s1 s2 s3,
CCstep s1 s2 -> star s2 s3 -> plus s1 s3.

Lemma match_find_label_None:
forall lbl s1 k0 k0',      match_cont (strip_skip k0)  (strip_skip' k0') ->
find_label lbl s1 k0 = None -> CC.find_label lbl s1 k0' = None
with match_find_ls_None:
forall lbl ls k0 k0',  match_cont (strip_skip k0)  (strip_skip' k0') ->
find_label_ls lbl ls k0 = None -> CC.find_label_ls lbl ls k0' = None.