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

Lemma match_cont_call_strip: forall k k', call_cont k <> nil -> match_cont (strip_skip k) (strip_skip' k') -> match_cont (Kseq (Sreturn None) :: call_cont k) (CC.call_cont k').