Ltac Cong := auto 4 with cong.Ltac eCong := eauto with cong.

Lemma cong3_transitivity : forall A0 B0 C0 A1 B1 C1 A2 B2 C2, Cong_3 A0 B0 C0 A1 B1 C1 -> Cong_3 A1 B1 C1 A2 B2 C2 -> Cong_3 A0 B0 C0 A2 B2 C2.