new A → (F ∧ G → (F ∧ A → (G ∧ G → (((B → A) → A) → (C ∧ F → C) ∨ G))))
intro
intro
cases 1
intro
cases 4
intro
cases 7
intro
cases 1
cases 4
cases 7
left
intro
cases 17
cases 1
cases 4
cases 7
cases 17
exact 18