| count(a, bag1) = 0, count(a0, bag0 ++ a) < count(a0, bag1) ⊦ 0 = count(a0, (bag0 \ bag1) ++ a), count(a0, bag1) = 0 |
⊦ count(a, bag ++ b) = (a = b ⊃ 1;0) + count(a, bag)
count(a, bag1) = 0, (a0 = a ⊃ 1;0) + count(a0, bag0) < count(a0, bag1) ⊦ 0 = count(a0, (bag0 \ bag1) ++ a), count(a0, bag1) = 0
Used terms: a, bag0, a0