1 / 2 1 / 3 1 / 6 1 / 7 () () find the law

1 / 2 1 / 3 1 / 6 1 / 7 () () find the law

1 / 2 1 / 3 1 / 6 1 / 7 (1 / 10) (1 / 11) The second group: 1 / 3, 1 / 7, 1 / 11