new (D ∨ E → D) → (B ∧ C → (A ∧ E → (D → (A → (C ∧ F → B ∧ ((B ∧ D) ∧ (F → A)))))))
intro
intro
cases 1
intro
cases 4
intro
intro
intro
cases 9
cases 1
cases 4
cases 9
constructor
exact 2
constructor
constructor
exact 2
exact 7
intro
cases 1
cases 4
cases 9
exact 5