new (F ∨ E → D) → (((D → B) → D) → (G ∧ E → ((D → F) → ((E → B) → ((G → C) → (((A → F) → E) → (C ∨ E) ∨ D))))))
intro
intro
intro
cases 2
intro
intro
intro
intro
cases 2
left
left
apply 7
exact 3