22. How many different positions can appear on a chessboard if both players, starting from the initial position, make only one move each?
22. In the initial position, each pawn and each knight can move in two ways, while the other pieces cannot make a move. Therefore, from the initial position, 20 different moves can be made by both the white and black pieces. Thus, after each player makes one move, $20 \cdot 20=400$ different positions can result.