new B ∨ A → (A → (B → ((A → B) → ((((B ∨ C) ∧ (A ∨ B)) ∧ A ∨ (D ∨ B ∧ A)) ∨ B) ∧ B)))
intro
intro
intro
intro
constructor
left
left
constructor
constructor
left
exact 2
left
exact 1
exact 1
exact 2