while True:
	H, W = map(int, raw_input().split())
	if H == 0 and W == 0:
		break
	else:
		x = '.'
		y = '#'
		for k in range(0, H):
			x,y = y,x
			if W%2 == 0:
				print (x+y) * (W/2)
			elif W%2 != 0:
				print (x+y) * (W/2) + x
		print ''