Goal:
  
  A : Type
  P : nat → A → A → Type
  Q : nat → A → A → Type
  i : nat
  l : list A
  l' : list A
  ============================
   (OnOne2i P i l l'
    → (∀ (i : nat) (x y : A), P i x y → Q i x y) → OnOne2i Q i l l')


DEBUG:Going to execute:
induction 1; constructor