intro f
⊢ ∀ {f g : Multiset ℕ}, (∀ x ∈ f, OddPrimeOrFour x) → (∀ x ∈ g, OddPrimeOrFour x) → f.prod = g.prod → f = g
f : Multiset ℕ
⊢ ∀ {g : Multiset ℕ}, (∀ x ∈ f, OddPrimeOrFour x) → (∀ x ∈ g, OddPrimeOrFour x) → f.prod = g.prod → f = g