new D ∧ C → (A ∨ (B ∨ F) → (B ∧ A → (F → (E ∨ (E → D) ∧ B) ∧ A ∨ (A ∨ (E → A) ∧ C → E))))
intro
cases 0
intro
intro
cases 4
intro
cases 0
cases 4
left
constructor
right
constructor
intro
cases 0
cases 4
exact 1
exact 5
exact 6