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

Lemma resource_at_join2:
forall phi1 phi2 phi3,
level phi1 = level phi3 -> level phi2 = level phi3 ->
(forall loc, join (phi1@loc) (phi2@loc) (phi3@loc)) ->
join (ghost_of phi1) (ghost_of phi2) (ghost_of phi3) ->
join phi1 phi2 phi3.