import sys
def ask(Y):
	print "? %d" % Y
	sys.stdout.flush()
	res = int(raw_input())
	return res

res = ask(100)
if res == 0:
	print "! %d" % 100
elif res == -1:
	for i in range(99):
		if ask(0) == 0:
			print "! %d" % (i+1)
			break
else:
	left = 100
	right = 10**9 + 1
	for i in range(99):
		mid = (left + right) / 2
		res = ask(mid)
		if res == 0:
			print "! %d" % (i+1+mid)
			break
		elif res == -1:
			left -= 1
			right = mid - 1
		else:
			left = mid - 1
			right -= 1