proposition: Lemma Dyck_lp_auxK l: Dyck_irred l -> Dyck_rp_aux(Dyck_lp_aux l) = l.
proof: Proof. by move => /andP[/eqP pa _]; rewrite / Dyck_rp_aux/Dyck_lp_aux /= drop0 - pa. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype) mathcomp(ssrnat seq path div) mathcomp(fintype tuple finfun bigop finset binomial)