proposition: Lemma Sperner_6: order_length r (csucc n).
proof: Proof. split; last by apply:Sperner_4. have: n \Eq E by apply/card_eqP; rewrite /n double_cardinal. move/ (equipotent_ex_pr) /Sperner_5 /Zo_P=> [fa fb]; ex_tac. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)