proposition: Lemma perm_sort_leP s1 s2 : reflect (sort <=%O s1 = sort <=%O s2) (perm_eq s1 s2).
proof: Proof. exact/perm_sortP/le_anti/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)