The magician has a small money box, which can be loaded with one yuan or 50 fen coins, and borrow one dollar and 50 fen coins to the audience, then the magician turns,
and the spectators put the coin in according to their own preferences, put the box on the table, the other is hidden, and the magician is based on the telepathy without
touching the box. You can guess if the audience put in one yuan or 50 Fen. A magic box.