import sys

def puts(s):
    print s
    sys.stdout.flush()

l, r = 10, 10 ** 9
while 1:
    x = (l + r) / 2
    
    puts("? %d" % x)
    reply = raw_input()
    if reply == 1:
        l = x
    if reply == -1:
        r = x
    if reply == 0:
        puts("! %d" % (max(0, x - 1)))
        break

    l, r = max(0, l - 1), max(0, r - 1)