∀ {v : Lean.Level} {M : Q(Type v)} (a₁ : ℤ) (x₁ : Q(«$M»)) (k₁ : ℕ) (t₁ : List ((ℤ × Q(«$M»)) × ℕ)) (a₂ : ℤ)
  (x₂ : Q(«$M»)) (k₂ : ℕ) (t₂ : List ((ℤ × Q(«$M»)) × ℕ)),
  (invImage (fun x => PSigma.casesOn x fun a a_1 => (a, a_1)) Prod.instWellFoundedRelation).1 ⟨((a₁, x₁), k₁) :: t₁, t₂⟩
    ⟨((a₁, x₁), k₁) :: t₁, ((a₂, x₂), k₂) :: t₂⟩