while True:
	h,w=map(int,input().split())
	if h==0 and w==0:
		break
		
	for i in range(h):
		for j in range(w):
			if (i%2==0 and j%2==0) or (i%2==1 and j%2==1):
				print("#",end="")
			else:
				print(".",end="")
		print("")
	print("")
			
