Proof using.
induction l; intros; simpl in *; intuition.
break_if; auto.
do_bool.
eapply IHl; eauto.
eapply cons_contiguous_sorted; eauto.
simpl; intuition.
Qed.

(* Specifications: *)
Lemma sorted_NoDup :
forall l,
sorted l -> NoDup l.