20
.......x.....x.x..x.
x....x............o.
x.x.......o.x......o
......x.xo..oo...x.o
....xo.....x........
.o.o...xx....x...o.x
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........x.....ox....
....................
x...xoo..x..x.......
oxxx................
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.o........o.o.o.....
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x....x.........ox.x.
............o..x.x..
........xo..........
.......oo....x.....o
...x.o....o.....x.oo
