One of the Elves found this problem on a fabulous puzzle list maintained by Phillip Thomas at U. Mass. I won’t put the link in case it encourages you to jump straight to the solution there, but you should be able to find it for yourself if you get stuck. I will post Phillip’s solution with next Sunday’s puzzle.
You are in a completely dark room. I dump a bag of 1017 Othello chips on the floor. These chips are black on one side and white on the other. You can feel around for the chips, but you cannot see which side is up because it is dark. I tell you that exactly 23 have the black side up. I ask you to divide the chips into two piles (every chip must be in one [and only one] of the piles) such that the two piles have the same number of chips with the black side up (they may have different numbers of chips with the white side up). How do you do it?