| ∀ n. (∀ n0. count(n0, (bag0 -- n) ++ n) = count(n0, bag0)) ↔ count(n, bag0) ≠ 0 ⊦ (n = m ⊃ 1;0) + count(n, bag0) = 0, ∀ n0. count(n0, (m = n ⊃ bag0;(bag0 -- n) ++ m) ++ n) = count(n0, bag0 ++ m) |
∀ n. (∀ n0. count(n0, (bag0 -- n) ++ n) = count(n0, bag0)) ↔ count(n, bag0) ≠ 0 ⊦ (n = m ⊃ 1;0) + count(n, bag0) = 0, count(n0, (m = n ⊃ bag0;(bag0 -- n) ++ m) ++ n) = count(n0, bag0 ++ m)