# -*- coding:utf-8 -*-
import sys

if __name__ == "__main__":
	minimum = 1
	maximum = 10 ** 9
	for i in xrange(100):
		mid = (maximum - minimum) / 2 + minimum
		print "? %d" % mid
		sys.stdout.flush()
		result = input()
		if result == 1:
			minimum = mid
		else:
			maximum = mid
		if maximum == minimum:
			print "! %d" % maximum
			sys.stdout.flush()
			exit()
		elif maximum - minimum == 1:
			print "? %d" % maximum
			sys.stdout.flush()
			result = input()
			if result == 1:
				print "! %d" % maximum
				sys.stdout.flush()
				exit()
			else:
				print "! %d" % minimum
				sys.stdout.flush()
				exit()