⊦ perm(ints, ints0) → Π ints = Π ints0
perm(ints, ints0) → Π ints = Π ints0, ∀ i. i ∈ ints ↔ i ∈ ints0 ⊦ Π ints = Π ints0, dups(ints), dups(ints0)
Used terms: ints, ints0