import sys

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

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

if res == 0 :
	print(1000)
	sys.exit()

if res == -1 :
	high = mid
	mid = (low + high) // 2 - 1
else :
	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()
			break

		elif res == -1 :
			high = mid

		else :
			low = mid

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