.
To solve the problem, I will assume that 10 pairs of B-shoes are different (distinguishable), as well as 12 pairs of L-shoes, too.
Actually, the problem, had it be formulated correctly, should say it directly, openly and explicitly,
without my deciphering/remaindering.
But since the problem is worded UNPROFESSIONALLY, forced to do it, instead of the composer to this problem.
In the worst case, you will pick up 10 + 12 = 22 unpaired shoes;
but the next, 23-rd shoe will give you a pair, inevitably.
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Solved.
For many other similar solved problems, see the lesson
- In the worst case
in this site.