6.6. A rectangular chocolate bar is divided into a grid of $17 \times 17$ squares by grooves. Two players, A and B, play a game according to the following rules: each player, on their turn, divides one rectangular piece of chocolate into two smaller rectangles (only along the grooves). After B's turn, B immediately eats one of the two pieces he has just created. The player who cannot make a move loses. A starts the game. Assuming both players use the optimal strategy, who will win?
6.6. Under the correct strategy, B will win.

In order to win, B should ensure that after each of their moves, all pieces of chocolate are rectangles with all sides of odd length. It should be noted: at the beginning, the $17 \times 17$ chocolate block meets this requirement. Afterwards, after each of A's moves, there will be 1 piece of chocolate with one side of even length (the other side being odd, and the rest of the chocolate pieces being rectangles with all sides of odd length). Thus, B can divide this 1 piece of chocolate into rectangles with all sides of odd length. Therefore, B can always make their move. As shown in Figure 7.