new (C → A) → ((D → A) → (D → (E ∧ D → ((E → C) → (C → ((B → C) → E)) ∨ (D ∧ B ∨ A) ∧ (F → A)))))
intro
intro
intro
intro
cases 3
intro
cases 3
left
intro
cases 3
intro
cases 3
exact 4