while True:
	flag = 0
	line = input().split()
	h = int(line[0])
	w = int(line[1])
	
	if h == 0 and w == 0:
		break
	
	for i in range(h):
		if i % 2 == 0:
			for j in range(w):
				if(j%2==0):
					print("#",end='')
				else:
					print(".",end='')
		else:
			for j in range(w):
				if(j%2==0):
					print(".",end='')
				else:
					print("#",end='')
		print()
                print()
