Goal:
    A : Type  f : nat → A  m : nat  IHm : #|unfold m f| = m
  ============================
   (#|unfold m f| + 1 = S m)


DEBUG:Going to execute:
intros; Zify.zify_pre_hook; zify_elim_let; zify_op;
            Zify.zify_iter_specs