I recently got hold of an English translation of Boris A. Kordemsky’s The Moscow Puzzles: 359 Mathematical Recreations, which was first published in 1956. In American mathematics and science writer Martin Gardner’s introduction, the book was said to be “the best and most popular puzzle book ever published in the Soviet Union.” Being a fan of brain teasers myself, I immediately flipped through its pages and was surprised that I was already familiar with some of the puzzles involving matches and coins, some of them I learned from my brother and my father. What struck me the most, however, is the puzzle I found I remembered to have been taught me by my own mother.