http://judge.mipt.ru/mipt_cs_on_python3/labs/lab2.html
 n = 0
	if cell_is_filled():
		while not wall_is_on_the_right():
			n += 1
			for i in range(n):
				move_right()
	else:
		while not wall_is_on_the_right():
			move_right()