new D ∧ E → (((D → E) → F) → (((H → D) → D) → (((H → C) → E) → ((F → D ∧ I) → (C ∧ C → F) ∨ H))))
intro
cases 0
intro
intro
intro
intro
cases 0
left
intro
cases 9
cases 0
cases 9
apply 3
intro
cases 0
cases 9
exact 2