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