proposition: Lemma nth_error_app: forall {T} (al bl : list T) (j: nat), nth_error (al++bl) (length al + j) = nth_error bl j.
proof: Proof. intros. induction al; simpl; auto. 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