new C ∨ B → (A ∧ B → ((D ∨ A → B) → (((B → C) → C) → (E ∧ B → A ∧ ((C → D) → E ∨ D)))))
intro
intro
cases 1
intro
intro
intro
cases 6
cases 1
cases 6
constructor
exact 2
intro
cases 1
cases 6
left
exact 7