import sys

l = 1
r = 10 ** 9 + 1

while r - l > 1:
    pos = (r + l) // 2
    print ("? %d" % pos)
    sys.stdout.flush()
    flg = int(input())
    if flg:
        r = pos
    else:
        l = pos
print("! %d" % r)