proposition: Lemma lezN_nat m n : (m%:Z <= - n%:Z) = (m == 0) && (n == 0).
proof: Proof. by move: m n=> [|?] []. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)