lt_list = []
gt_list = []

d = 5*(10**8)
d1 = 5*(10**8)

for i in range(99):
	ans = -1
	for i in lt_list:
		if i+1 in gt_list:
			ans = i
	
	if ans == -1:
		print("? "+str(d))
		res = int(input())
		d1 = max(d1//2 , 1)

		if res == 1:
			lt_list.append(d)
			d = d + d1
		else:
			gt_list.append(d)
			d = d - d1

	else:
		print("! "+str(ans))