proposition: Lemma InEither_app_iff: forall a l1 l2, InEither a (l1 ++ l2) <-> InEither a l1 \/ InEither a l2.
proof: Proof. intros a l1. revert a. induction l1; simpl; intros. 1: intuition. rewrite !InEither_cons_iff, IHl1. intuition. Qed.
imports: Coq.Lists.List Coq.micromega.Lia Coq.Sorting.Permutation Coq.ZArith.ZArith_base Coq.ZArith.Zcomplements Coq.Logic.FunctionalExtensionality CertiGraph.lib.Coqlib CertiGraph.lib.EquivDec_ext VST.zlist.sublist VST.zlist.list_solver