new D → ((C ∨ D → A) → (A ∨ F → ((D → E) → ((B ∧ F) ∧ F → (C → (D → D ∧ D))))))
intro
intro
intro
intro
intro
cases 4
intro
cases 4
cases 5
cases 8
intro
cases 4
cases 5
cases 8
cases 15
constructor
exact 0
exact 0