new C → ((B → A ∧ A) → (G ∧ E → ((C → E ∧ D) → ((F → A) → (G → ((A → G) → (F ∨ G) ∨ (E ∧ F → (F → C))) ∨ E)))))
intro
intro
intro
cases 2
intro
intro
cases 2
intro
cases 2
left
intro
cases 2
left
right
exact 3