DB 这么廉价
.....灌........灌......
....灌..灌.....灌.灌.....
.....灌..灌....灌..灌....
......灌..灌..灌.灌.灌.... .
.....灌......... 灌....
...灌.............灌...
..灌...............灌..
.灌.................灌.
灌...................灌
灌...................灌
灌.....∩.......∩.....灌
灌. ..................灌
灌. ...◎....U....◎....灌
.灌.................灌.
..灌灌.............灌灌..
....灌.灌.灌.灌.灌.灌.灌...