∀ {as bs : ByteArray} {i j : ℕ} (len : ℕ) (hi : i + (len + 1) ≤ as.size) (hj : j + (len + 1) ≤ bs.size)
  (motive : (∀ (k : ℕ) (hk : k < len), as[i + k] = bs[j + k]) ∧ as[i + len] = bs[j + len] → Prop)
  (x : (∀ (k : ℕ) (hk : k < len), as[i + k] = bs[j + k]) ∧ as[i + len] = bs[j + len]),
  (∀ (h : ∀ (k : ℕ) (hk : k < len), as[i + k] = bs[j + k]) (h' : as[i + len] = bs[j + len]), motive ⋯) → motive x