while True:
	H, W = map(int, input().split())
	if H == 0 and W == 0:
		break	
	countl = 0
	
	while True:
		if W == 0:
			break
		if countl == H:
			break
		elif countl % 2 == 0:
			countll = 0
			while True:
				if countll % 2 == 0:
					print('#', end='')
					countll += 1
				else:
					print('.', end='')
					countll += 1
				if countll == W:
					print()
					break
		elif countl % 2 == 1:
			countll = 0
			while True:
				if countll % 2 == 0:
					print('.', end='')
					countll += 1
				else:
					print('#', end='')
					countll += 1
				if countll == W:
					print()
					break
		countl += 1
print() 