Dan and Sam play a game on a \(5\times5\times5\) cube that consists of 125 objects; each one must take at least one object and at most a whole heap, in his turn.
As an explicit example, in the first turn, Dan can take just the bottom front left corner object, or the whole vertical central heap, or the whole bottom front horizontal heap. Thus, he can take any number of objects of one of the 125 initial heaps (heaps cannot be diagonals).
The winner is the one who takes the last object. If Dan begins, who will win? This means, who has a winning strategy?