| 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 |
count(n0, bag) - (n0 = n ⊃ 1;0) = 0, ∀ n2. count(n2, bag -- n) = 0 ⊦ count(n0, bag) = 0, count(n1, bag) = count(n1, ∅ ++ n)