x, y = map(int, input().split())
while not(x == 0 and y == 0):
	for i in range(x):
		for j in range(y):
			if (i+j)%2 == 0:
				print('#', end = '')
			else:
				print('.', end = '')
		print()
	print()
	x, y = map(int, input().split())
