have hl (acc : Array (Literal (PosFin n)) × Array Assignment × Bool)
  (h : ∃ hsize : acc.2.1.size = n, acc.2.2 → ∃ j : PosFin n, acc.2.1[j.1]'(by rw [hsize]; exact j.2.2) = both)
  (l' : Literal (PosFin n)) (_ : l' ∈ l) :
  let insertUnit_res := insertUnit acc l'
  ∃ hsize : insertUnit_res.2.1.size = n,
    insertUnit_res.2.2 → ∃ j : PosFin n, insertUnit_res.2.1[j.1]'(by rw [hsize]; exact j.2.2) = both := by
  intro insertUnit_res
  have hsize : insertUnit_res.2.1.size = n := by rw [insertUnit_preserves_size, h.1]
  apply Exists.intro hsize
  intro insertUnit_res_success
  rcases h with ⟨acc_size, h⟩
  exact contradiction_of_insertUnit_success acc.2.1 acc_size acc.1 acc.2.2 l' h insertUnit_res_success
n : Nat
assignments : Array Assignment
assignments_size : assignments.size = n
units : Array (Literal (PosFin n))
foundContradiction : Bool
l : List (Literal (PosFin n))
insertUnit_fold_res : Array (Literal (PosFin n)) × Array Assignment × Bool :=
  List.foldl insertUnit (units, assignments, foundContradiction) l
h0 : foundContradiction = true → ∃ i, assignments[i.val] = both
insertUnit_fold_success : insertUnit_fold_res.snd.snd = true
acc0 : Array (Literal (PosFin n)) × Array Assignment × Bool := (units, assignments, foundContradiction)
hb : ∃ _hsize, acc0.snd.snd = true → ∃ j, acc0.snd.fst[j.val] = both
⊢ ∃ j, insertUnit_fold_res.snd.fst[j.val] = both
n : Nat
assignments : Array Assignment
assignments_size : assignments.size = n
units : Array (Literal (PosFin n))
foundContradiction : Bool
l : List (Literal (PosFin n))
insertUnit_fold_res : Array (Literal (PosFin n)) × Array Assignment × Bool :=
  List.foldl insertUnit (units, assignments, foundContradiction) l
h0 : foundContradiction = true → ∃ i, assignments[i.val] = both
insertUnit_fold_success : insertUnit_fold_res.snd.snd = true
acc0 : Array (Literal (PosFin n)) × Array Assignment × Bool := (units, assignments, foundContradiction)
hb : ∃ _hsize, acc0.snd.snd = true → ∃ j, acc0.snd.fst[j.val] = both
hl :
  ∀ (acc : Array (Literal (PosFin n)) × Array Assignment × Bool),
    (∃ hsize, acc.snd.snd = true → ∃ j, acc.snd.fst[j.val] = both) →
      ∀ (l' : Literal (PosFin n)),
        l' ∈ l →
          let insertUnit_res := insertUnit acc l';
          ∃ hsize, insertUnit_res.snd.snd = true → ∃ j, insertUnit_res.snd.fst[j.val] = both
⊢ ∃ j, insertUnit_fold_res.snd.fst[j.val] = both