proposition: Lemma ep_in_en : ep \in en.
proof: Proof. move/andP: Hcond => [_]. by rewrite /step_end_cond !inE => /andP [_] ->. Qed.
imports: mathcomp(all_ssreflect ssralg fingroup zmodp poly ssrnum) mathcomp(matrix perm) ssr_ext ssralg_ext fdist subgraph_partition tanner