# (c) midandfeed
while(True):
	h, w = [int(x) for x in input().split()]
	
	if (h == 0) and (w==0):
		break
		
	col = "#."*w
	for i in range(1, h+1):
		if (i&1):
			print(col[0:w])
		else:
			print(col[1:w+1])
	print()		
	