proposition: Lemma is_part_conj sh : is_part sh -> is_part (conj_part sh).
proof: Proof. elim: sh => //= s0 sh IHsh /= /andP[_ {}/IHsh]. exact: is_part_incr_first_n. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype