proposition: Lemma nExist (T : System) (f : Formula) (v : nat): SysPrf T (allH v, ~ f)%nt -> SysPrf T (~ (exH v, f))%nt.
proof: Proof. apply (nExist LNT). Qed.
imports: Coq(Arith Ensembles List) hydras.Ackermann(Languages folProof folProp folLogic3)