while True:
	H ,W = map(int,input().split())
	if H * W == 0 : 
		break
	else:
		a = '#'*W
		a = list(a)
		b = '.'*W
		b = list(b)
		for i in range(W):
			if not(i % 2):
				a[i] = '.'
				b[i] = '#'
	for i in range(H):
		if i % 2 :
			print("".join(a))
		else:
			print("".join(b)) 
