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