| count(n0, bag -- n) = 0, ∀ n2. count(n2, bag -- n) = 0 ⊦ count(n0, bag) = 0, count(n1, bag) = count(n1, ∅ ++ n) |
⊦ count(n, bag0 -- n0) = count(n, bag0) - (n = n0 ∧ count(n, bag0) ≠ 0 ⊃ 1;0)
count(n0, bag) - (n0 = n ∧ count(n0, bag) ≠ 0 ⊃ 1;0) = 0, ∀ n2. count(n2, bag -- n) = 0 ⊦ count(n1, bag) = count(n1, ∅ ++ n), count(n0, bag) = 0
Used terms: n, bag, n0