Module R := R0.
Hint Resolve (@subp_sepcon _ Join_rmap Perm_rmap Sep_rmap): contractive.

Lemma ghost_same_level_gen:
forall n a b c, join (ghost_fmap (approx n) (approx n) a) (ghost_fmap (approx n) (approx n) b) c ->
ghost_fmap (approx n) (approx n) c = c.