proposition: Lemma mem2_sort_le s x y : x <= y -> mem2 s x y -> mem2 (sort <=%O s) x y.
proof: Proof. exact/mem2_sort/le_trans/le_total. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)