obtain ⟨t2, rfl⟩ := Multiset.exists_cons_of_mem this
case neg.intro
p : ℤ√(-3)
him : ¬p.im = 0
this✝ : star p ≠ p
t1 : Multiset (ℤ√(-3))
hcoprime : IsCoprime (Multiset.prod (p ::ₘ t1)).re (Multiset.prod (p ::ₘ t1)).im
h1 : p ∈ p ::ₘ t1
h2 : star p ∈ p ::ₘ t1
this : star p ∈ t1
⊢ IsUnit p
case neg.intro.intro
p : ℤ√(-3)
him : ¬p.im = 0
this✝ : star p ≠ p
t2 : Multiset (ℤ√(-3))
hcoprime : IsCoprime (Multiset.prod (p ::ₘ star p ::ₘ t2)).re (Multiset.prod (p ::ₘ star p ::ₘ t2)).im
h1 : p ∈ p ::ₘ star p ::ₘ t2
h2 : star p ∈ p ::ₘ star p ::ₘ t2
this : star p ∈ star p ::ₘ t2
⊢ IsUnit p