End step.
Implicit Arguments stepS [state step cont s k s' k' n].
Inductive prog_star : state -> prog -> state -> cont -> Prop :=
| star_prog : forall P s k s' k',
P 0%N = Some k -> star (step P) s k s' k' ->
prog_star s P s' k'.
(** interpreter is sound *)

Lemma stepN_Ksafe n P (s : state) : stepN (step P) n s Ksafe s Ksafe.