proposition: Lemma is_part_rconsK sh sn : is_part (rcons sh sn) -> is_part sh.
proof: Proof. exact/is_part_subseq/subseq_rcons. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype