Consider the following premises. p -> u. ~q. q -> u. u -> q. u <-> p. Can we infer p from them?
 From u -> q, q -> u we can infer u <-> q. From u <-> p we can infer u -> p. From u -> p, p -> u we can infer u <-> p. From u <-> q, ~q we can infer ~u. Finally, from u <-> p, ~u we can infer ~p, which contradicts p. Therefore, the answer is no.