new D → (C ∧ A → ((E → A ∧ A) → ((D → B) → (E → (E ∧ D → (E ∧ A) ∧ ((C ∨ C) ∨ C)) ∧ C))))
intro
intro
cases 1
intro
intro
intro
cases 1
constructor
intro
cases 9
cases 1
cases 9
constructor
constructor
exact 6
exact 3
left
left
exact 2
exact 2