new B → (B ∧ F → (F ∧ I → (B → ((H → D ∧ G) → (((C → F) → (E ∨ E) ∨ F) → ((F → A ∧ H) → ((E → G) ∨ G) ∨ (I ∨ D)))))))
intro
intro
cases 1
intro
cases 4
intro
intro
intro
intro
cases 1
cases 4
right
left
exact 6