while True:
	a, b = map(int, input().split())
	if a == 0 and b == 0:
		exit()
	for i in range(0,a):
		for j in range(0,b):
			if (i+j)%2 == 0:
				print('#', end='')
			else:
				print('.', end='')
		print()
	print()
