//打印数据如下：

//$a1:

Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 4
[5] => 5
[6] => 6
)

//$a2:
Array
(
[0] => 2
[1] => 2
[2] => 2
[3] => 2
)

//$a3:
Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
)

//$a4:
Array
(
[0] => -2
[1] => -1
[2] => 3
[3] => 3
[4] => 5
[5] => 7
[6] => 8
[7] => 9
[8] => 9
)