∀ {R : Type u} [inst : CommRing R] {p : ℕ} [inst_1 : Fact (Nat.Prime p)] [inst_2 : Fact ¬IsUnit ↑p]
  [inst_3 : IsAdicComplete (Ideal.span {↑p}) R] (x : PreTilt R p),
  (WittVector.fontaineTheta R p) ((WittVector.teichmuller p) x) = PreTilt.untilt x