new ((B → E) → D) → ((D → E) → ((A → E) → (C ∨ E → C ∨ ((C ∨ D) ∨ ((C ∨ A) ∨ (C ∨ A))))))
intro
intro
intro
intro
right
left
cases 3
left
exact 4
right
apply 0
intro
exact 5