20
...o....x..x........
x...........x..x..x.
...........o.xoo....
oxo...o...........o.
ox.....x.ox..o..o.x.
...ooo...x......x...
..o....x.....o...o.x
o.oo.o...x..........
o..o..o.....o....o..
........o.........x.
..x.o..xxx..........
xx.x...x...o...x.x..
...............x....
.o.......x..x.....o.
...........x....x..x
....o...............
..x....x.x..........
.............o.o....
...........x....xo..
.x.o.........o.oo...
