∀ {D : Type u_5} [inst : CategoryTheory.Category.{v_5, u_5} D] [inst_1 : CategoryTheory.Preadditive D]
  [inst_2 : CategoryTheory.HasShift D ℤ] [inst_3 : ∀ (n : ℤ), (CategoryTheory.shiftFunctor D n).Additive] (m n : ℤ × ℤ),
  CategoryTheory.CommShift₂Setup.int.z m n = (-1) ^ (m.1 * n.2)