b a x b a y0 y1 y2 0 0 0 0 0 1 1 0 1 1 0 0 1 0 0 0 0 0 2 0 1 0 0 1 0 1 0 3 0 1 1 1 0 1 0 0 4 1 0 0 0 0 0 0 0 5 1 0 1 1 0 0 1 1 6 1 1 0 0 1 1 0 1 7 1 1 1 1 0 1 1 0