# -*- coding: utf-8 -*-

import sys
top = 10 ** 9
bottom = 1
while True:
    mid = (top + bottom) / 2
    print "? %d" % (mid)
    sys.stdout.flush()
    res = int(input())
    if res == 1:
        bottom = mid
    else:
        top = mid
    if bottom + 1 >= top:
        break

print "! %d" % (bottom)
sys.stdout.flush()