P := [m,n] -> { [x,y] : x, y >= 0 and 2x <= n and 3x + 4y <= m };
R := lattice_width(P);
W := [m, n] -> { 1/2 * n : m >= 0 and 0 <= n <= 2m and 2n < m and 3n < 2m;
		1/4 * m : m >= 0 and n >= 0 and 2n >= m };
Z := [n] -> { };
assert((R - W) == Z);
