10 black socks, 8 white socks, and 3 blue socks are in your drawer. The room is pitch dark. If you take socks out one at a time, how many socks might you need to remove until you can be sure that you're holding at least two socks of the same color?
If you take out four socks, at least two must match.
The first three can be of different colors but you can't have four socks that are different from one another.
The number of socks of each color does not affect the answer.