while 1:
	H, W = map(int, raw_input().split())
	if (H == 0 and W == 0):
	break

	for i in range(H):	
		if i%2==0:
			for j in range(W):
				if j%2==0:
					print "#",
				elif:
					print ".",
			print ""
		elif:
			for j in range(W):
				if j%2==0:
					print ".",
				elif:
					print "#",
			print ""