proposition: Lemma lteifNE x y C : x < y ?<= if ~~ C = ~~ (y < x ?<= if C).
proof: Proof. by case: C => /=; case: leP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)