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