(** Exploiting determinacy *)

Remark silent_or_not_silent:
  forall t, t = E0 \/ t <> E0.

Lemma f2b_determinacy_star: forall s s1, Star L2 s E0 s1 -> forall t s2 s3, Step L2 s1 t s2 -> t <> E0 -> Star L2 s t s3 -> Star L2 s1 t s3.