. ... .. ... . .. . . #. # ..# .##. ##..##.. # ..............# . ... ...... .. . .. # . #. ## . ##. .##..##..##..#...# ....... . .....## . #............. ..# .##..#.##..##..##. #..# .......##..##..##..# . .. ............... .. # #.. #..#................# #..##..#.##..## .##..##.# ∆.......##..##..# . # # ................... . #. ##..#v.............# ##..##..#.##..##..##. # ...........#.v##..## ..# . ........v......... . . ##..##..#........ .. # #..#.##..##.. .....# ..# .. ....... ...∆ ........ .. .#......## x###...#.#