1:0
2:99
3:198
4:297
5:396
6:495
7:594
8:693
9:792
10:990
11:999
12:1188
13:1485
14:1980
15:1998
16:2475
17:2970
18:2997
19:3960
20:3996
21:4950
22:4995
23:5940
24:5994
25:6930
26:6993
27:7920
28:7992
29:8991
30:9900
31:9990
32:9999.
这个四位数为 9999