proposition: Lemma BZor_tor: total_order BZ_order.
proof: Proof. move:BZ_order_aux1 => h1. move: (worder_total (proj1 Nat_order_wor)) => h2. apply:orsum2_totalorder => //. by apply:total_order_opposite; apply:total_order_sub. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)