while 1:
	a = ""
	b = ""
	H, W = map(int, input().split())

	if (H == 0 and W == 0) : break
	for i in range(W):
		if (i % 2 == 0) : a = a + "#"
		else : a = a + "."
	for i in range(W):
		if (i % 2 == 0) : b = b + "."
		else : b = b + ???#???

	for j in range(H):
		if j % 2 == 0: print(a)
		else : print(b)

	print()