new D ∨ A → ((G ∨ H → F) → (((H → E) → D) → ((H → D) → (A ∧ G → ((C → H) → (((B → H) → H) → ((C ∨ G → F) → ((G ∨ G) ∨ D → A) ∨ D)))))))
intro
intro
intro
intro
intro
cases 4
intro
intro
intro
cases 4
left
intro
cases 4
exact 5