new C → (B → ((F ∨ D → E) → ((C → F) → (D → ((D → A) → B ∧ (E ∧ E ∨ C))))))
intro
intro
intro
intro
intro
intro
constructor
exact 1
left
constructor
apply 2
left
apply 3
exact 0
apply 2
left
apply 3
exact 0