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

def ans(Y):
	print "! %d" % Y

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