⊦ count(n, bag0 ++ n0) = (n = n0 ⊃ 1;0) + count(n, bag0)
⊦ (n0 = n ⊃ 1;0) + count(n0, bag) = count(n0, bag ++ m ++ n), n0 = m
Used terms: n, bag, n0