proposition: Lemma lez1D x y : (1 + x <= y) = (x < y).
proof: Proof. by rewrite -subr_gt0 gtz0_ge1 lterBDr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)