induction n2; intuition; simpl in *.
destruct ls.
destruct n1; trivial.
trivial.
Qed.

(* Specifications: *)
Lemma evalDet_step_more_skipn : forall (A : Set)(c c' : Comp A) s s',
evalDet_step  c s = (cs_more c' s') ->
exists n, s' = skipn n s.