proposition: Lemma uniq_llen a l: sorted llen (a :: l) -> uniq l.
proof: Proof. by move/path_sorted => /sorted_llen_uniq. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path fintype div bigop binomial) mathcomp(prime finset ssralg ssrnum ssrint)