2, 4
2, 4, 2, 3, 4, 5, 6
2, 4, 2, 3, 4, 5, 6, 2, 3, 4, 5, 6, 7
2, 4, 2, 3, 4, 5, 6, 2, 3, 4, 5, 6, 7, 1, 2, 4, 5, 7