# ITP1_5_C
# チェスボードの描画

while 1:
	H, W = map(int, input().split())
	if H == W == 0:
		break
	for i in range(H):
		for j in range(W):
			if (i + j) % 2 == 0:
				print("#", end="")
			else:
				print(".", end="")
		print()
	print()

