new ((B → A) → D) → (C ∧ B → (D ∧ C → ((D ∨ B → ((((D → C) → (B → B)) → A) → C)) → B ∧ D)))
intro
intro
cases 1
intro
cases 4
cases 1
cases 4
intro
cases 1
cases 4
constructor
exact 3
exact 5