∀ {α : Type u_1} {s : Computation α} {a b : α} (motive : a ∈ s → b ∈ s → Prop) (x : a ∈ s) (x_1 : b ∈ s),
  (∀ (m : ℕ) (ha : some a = (↑s).get m) (n : ℕ) (hb : some b = (↑s).get n), motive ⋯ ⋯) → motive x x_1