new (E ∨ A → C) → ((B → A) → ((C → B) → ((E → G) → (E ∨ F → ((D → D ∨ C) → (B ∧ A → E ∨ ((G → F) ∨ B)))))))
intro
intro
intro
intro
intro
intro
intro
cases 6
cases 6
right
right
exact 7