forward.
apply andp_left1.
apply derives_refl.
Qed.

Lemma myprog_safe:  forall n, run myprog n <> None.
Definition run' (p: program) (n: nat) : bool :=
match
stepN p (nil, initial_heap p, Go (Const 0) (Const (boundary p) :: nil)) n
with None => false | _ => true
end.