import sys
l, r = 1, 10**9+1
while r - l > 1:
    c = (l+r)//2
    print ("? %d" % c)
    sys.stdout.flush()
    res = int(input())
    if res == 1:
        l = c
    else:
        r = c
print("! %d" % l)
sys.stdout.flush()