sizes (m, n) = [ (x, y) | x <- [1 .. 2 * m], y <- [1 .. 2 * n], x + y <= 2 * min m n ]
sizes (m, n) = [ (x, y) | x <- [1 .. 2 * m], y <- [1 .. 2 * n], x + y <= 2 * min m n ]
sizes (m, n) = [ (x, y) | x <- [1 .. 2 * m], y <- [1 .. 2 * n], x + y <= 2 * min m n ]