if wall_from_up() and wall_from_left():
move_down()
fill_cell()
move_right()
move_up()
fill_cell()
move_down()
elif wall_from_down() and wall_from_left():
move_right()
move_up()
fill_cell()
move_down()
elif wall_from_up() and wall_from_right():
move_down()
move_left()
fill_cell()
move_right()
elif wall_from_down() and wall_from_right():
move_up()
fill_cell()
move_left()
fill_cell()
move_right()