proposition: Lemma sgrz (n : int) : sgr n = sgz n.
proof: Proof. by rewrite sgrEz intz. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)