proposition: Lemma nth_error_app1: forall {T} (al bl : list T) (j: nat), (j < length al)%nat -> nth_error (al++bl) j = nth_error al j.
proof: Proof. intros. revert al H; induction j; destruct al; simpl; intros; auto; try lia. apply IHj. lia. 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