import sys
low,high = 0,10**9 + 1
while high - low > 1:
	mid = (high + low) >> 1
	print('? %d' % mid)
	sys.stdout.flush()
	ans = int(input())
	if ans == 1:
		low = mid
	else:
		high = mid
print('! %d' % low)
sys.stdout.flush()