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