Question 182
Mr. Fat moves around on the lattice points according to the following rules: From point $(x, y)$ he may move to any of the points $(y, x)$, $(3x, -2y)$, $(-2x, 3y)$, $(x+1, y+4)$ and $(x-1, y-4)$. Show that if he starts at $(0,1)$ he can never get to $(0,0)$.