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