kk=0
while kk==0:
	h,w=map(int,input().split())
	if h==0 and w==0:
		break
	else:
		for i in range(h):
			if i%2==0:
				s="#"
			else:
				s="."
			for k in range(w-1):
				if s[-1]=="#":
					s=s+"."
				else:
					s=s+"#"
			print(s)
		print("")


