new D → (H → (D ∧ H → (H → (G ∨ H → (D ∧ G → (((D → F) → G) → (B → A ∨ (B ∨ C))))))))
intro
intro
intro
cases 2
intro
intro
intro
cases 7
intro
intro
cases 2
cases 7
right
left
exact 11