intro a ha
case h.e'_2
x : ℕ
hx : ¬x = 0
⊢ ∀ a ∈ UniqueFactorizationMonoid.normalizedFactors x, 2 = a ∨ Odd a
case h.e'_2
x : ℕ
hx : ¬x = 0
a : ℕ
ha : a ∈ UniqueFactorizationMonoid.normalizedFactors x
⊢ 2 = a ∨ Odd a