∀ (k₁ : ℤ) (m₁ : Lean.Grind.CommRing.Mon) (p₁ : Lean.Grind.CommRing.Poly) (k₂ : ℤ) (m₂ : Lean.Grind.CommRing.Mon)
  (p₂ : Lean.Grind.CommRing.Poly),
  InvImage (fun x1 x2 => x1 < x2) (fun x => PSigma.casesOn x fun p₁ p₂ => sizeOf p₁ + sizeOf p₂) ⟨p₁, p₂⟩
    ⟨Lean.Grind.CommRing.Poly.add k₁ m₁ p₁, Lean.Grind.CommRing.Poly.add k₂ m₂ p₂⟩