Dan and Sam play a game on a \(9\times4\) grid; at the beginning, each one chooses either squares or circles, and, during the game, moves, in his turn, a single piece. Each piece can be moved only forward or backward, any number of squares (and cannot skip over the other pieces). This is the initial position:
A player loses when he is not able to move any of his pieces in his turn. If Dan begins, who will win? In other words, who has a winning strategy?