fact: Definition pairing f A := ∀ $0 ∈ shift 1 f → ∃ ∃ $1 ∈ shift 3 A ∧ $2 ≡ opair $1 $0.
imports: Undecidability.FOL.ZF Undecidability.FOL.Syntax.Facts Undecidability.FOL.Semantics.Tarski.FullFacts Undecidability.FOL.Sets.ZF Lia Undecidability.PCP(PCP Util.PCP_facts Reductions.PCPb_iff_dPCPb) Undecidability(Shared.ListAutomation)