have h0' : x ≠ 0 := by
  rintro rfl
  contradiction
a x : ℤ
hodd : Odd x
⊢ ∃ m c, c + m * x = a ∧ 2 * c.natAbs < x.natAbs
a x : ℤ
hodd : Odd x
h0' : x ≠ 0
⊢ ∃ m c, c + m * x = a ∧ 2 * c.natAbs < x.natAbs