# Congested Walkway

Dan and Sam play a game on a $4\times9$ grid, in which one takes squares (red) and the other takes circles (blue). Once the game starts, they take turns moving a single piece in their turn. Each piece can only be moved straight forward or backward, any number of grids (and cannot skip over the opponent's piece). This is the initial position:

A player loses when he is not able to move any of his pieces in his turn. If Dan goes first, who will win? In other words, who has a winning strategy?

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