new (G → D ∧ A) → (((G → A) → A) → (E ∧ H → (F ∧ E → ((C ∨ E → F) → (((H → G) → F) → ((D → H ∧ A) → (F → (B → A)) ∧ E ∨ ((A → E) ∨ (F ∨ G))))))))
intro
intro
intro
cases 2
intro
cases 5
intro
intro
intro
cases 2
cases 5
right
left
intro
cases 2
cases 5
exact 3