new (E ∨ C → C) → (E ∧ C → (C ∧ B → (D ∧ C → ((E ∨ G → G) → (B ∨ H → (A → (H ∨ B → (A ∨ G) ∨ B)))))))
intro
intro
cases 1
intro
cases 4
intro
cases 7
intro
intro
intro
cases 1
cases 4
cases 7
intro
cases 1
cases 4
cases 7
left
left
exact 12