new D → (C ∨ A → (B ∧ A → (((C ∨ B) ∧ (D → B)) ∧ C → (D → D))))
intro
intro
intro
cases 2
intro
cases 5
cases 2
cases 5
cases 6
cases 10
intro
cases 2
cases 5
cases 6
cases 10
cases 19
exact 0