left = 1
right = 1000000000

for i in range(100):
	mid = (left+right) // 2
	print("?",str(mid))
	res = int(input())
	if res == 1:
		print("?",str(mid+1))
		res = int(input())
		if res == 0:
			print("!",str(mid))
			break
		else:
			left = mid
	else:
		right = mid