import sys

low = 0
high = int(1e9 + 1)
mid = 1000
beforemid = 0
count = 0

print("?", mid)
sys.stdout.flush()
res = int(input())

if res == 0 :
	print("! 1000")
	sys.stdout.flush()

elif res == -1 :
	high = mid
	mid = (low + high) // 2 - 1

	while True :
		print("?", mid)
		sys.stdout.flush()
		res = int(input())
		count += 1

		if res == 0 :
			print("!", mid + count)
			sys.stdout.flush()
			sys.exit()

		elif res == -1 :
			high = mid

		else :
			low = mid

		beforemid = mid
		mid = (low + high) // 2 - 1

		if abs(mid - beforemid) < 5 :
			mid = min(mid, beforemid)

elif res == 1 :
	low = 900
	mid = (low + high) // 2 - 1

	while True :
		print("?", mid)
		sys.stdout.flush()
		res = int(input())
		count += 1

		if res == 0 :
			print("!", mid + count)
			sys.stdout.flush()
			sys.exit()

		elif res == -1 :
			high = mid

		else :
			low = mid

		beforemid = mid
		mid = (low + high) // 2 - 1

		if abs(mid - beforemid) < 5 :
			mid = min(mid, beforemid)