import sys

while True:
	data = map(int, raw_input().split())
	H = data[0]
	W = data[1]
	
	if H == 0 and W == 0:
		break
	else:
		for i in range(H):
			for j in range(W):
				if (i + j) % 2 == 0:
					sys.stdout.write("#")
				else:
					sys.stdout.write(".")
			print("")
		print("")