⊦ n ∈ bag0 ↔ count(n, bag0) ≠ 0
⊦ (∀ n. count(n, bag ++ m) ≤ 1) ↔ (∀ n. count(n, bag) ≤ 1) ∧ ¬ count(m, bag) ≠ 0
Used terms: bag, m