Hint Extern 1 (lc_co (g_AbsCong _ _ _)) =>
  let x1 := fresh in
  pick_fresh x1;
  apply (lc_g_AbsCong_exists x1).Hint Extern 1 (lc_co (g_CAbsCong _ _ _)) =>
  let c1 := fresh in
  pick_fresh c1;
  apply (lc_g_CAbsCong_exists c1).

Lemma open_tm_wrt_tm_rec_degree_tm_wrt_tm : forall a2 a1 n1, degree_tm_wrt_tm n1 a2 -> open_tm_wrt_tm_rec n1 a1 a2 = a2.