proposition: Lemma subseq_le_sorted s1 s2 : subseq s1 s2 -> sorted <=%O s2 -> sorted <=%O s1.
proof: Proof. exact/subseq_sorted/le_trans. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)