proposition: Lemma In_map_snd: forall {A B} a b (l: list (A * B)), In (a, b) l -> In b (map snd l).
proof: Proof. intros. assert (exists x, In (x, b) l) by (now exists a). now rewrite <- In_map_snd_iff in H0. 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