import sys

res = 1
l = 0
r = 1000000000+1
while l+1 < r:
    m = (l+r)/2
    print ("? %d" % m)
    sys.stdout.flush()
    res = int(input())
    if res == 1:
        l = m
    else:
        r = m
if res==1:
    print("! %d" % res)
else:
    print("! %d" % l)
sys.stdout.flush()