0, 4, 2, 4, 1, 5, 3, 5, 2, 6, 4, 6, 3, 7, 5, 7, 4, 8, 6, 8, 5, 9, 7, 9, 6, 10, 8, 10, 7, 11, 9, 11, 8, 12, 10, 12, 9, 13, 11, 13, 10, 14, 12, 14, 11, 15, 13, 15, 12, 16, 14, 16, 13, 17, 15, 17, 14, 18, 16, 18, 15, 19, 17, 19, 16, 20, 18, 20, 17, 21, 19, 21, 18