numMin=1
numMax=1000000001
while True:
	chkNum=int((numMin+numMax)/2);
	print("? {0}".format(chkNum),flush=True)
	if input()=="1": numMin=chkNum
	else: numMax=chkNum
	if numMin==numMax-1:
		print("! {0}".format(numMin),flush=True)
		break