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