apply tri.atMostOne
ℕ : Type
inst✝⁵ : Natural ℕ
ℤ : Type
inst✝⁴ : Core ℤ
inst✝³ : Addition ℤ
inst✝² : Multiplication ℤ
inst✝¹ : Negation ℤ
inst✝ : Sign ℤ
a : ℤ
tri : AA.ExactlyOneOfThree (a ≃ 0) (Positive a) (Negative a)
left✝ : a ≃ 0
right✝ : Nonzero a
⊢ False
ℕ : Type
inst✝⁵ : Natural ℕ
ℤ : Type
inst✝⁴ : Core ℤ
inst✝³ : Addition ℤ
inst✝² : Multiplication ℤ
inst✝¹ : Negation ℤ
inst✝ : Sign ℤ
a : ℤ
tri : AA.ExactlyOneOfThree (a ≃ 0) (Positive a) (Negative a)
left✝ : a ≃ 0
right✝ : Nonzero a
⊢ AA.TwoOfThree (a ≃ 0) (Positive a) (Negative a)