proposition: Lemma ltzD1 x y : (x < y + 1) = (x <= y).
proof: Proof. by rewrite -lezD1 lerD2r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)