for _ in range(int(input())):
	L, R = map(int, input().split())
	
	if R == 0:
		print(0)
		continue
	
	t = 0
	while R >> t:
		t += 1
	
	if 1 << (t - 1) <= L:
		print(-1)
	else:
		print((2 ** (t - 1) - 1) << (t - 1))