t = 1
print("? 30")
a = int(input())
if a == 0:
    print("! 30")
elif a == -1:
    while True:
        print("? 9")
        a = int(input())
        if a == 0:
            print("! " + str(9+t))
            break
        t += 1
else:
    ok = 30
    ng = 1000000000
    while True:
        mid = (ng+ok)//2
        if mid <= 0:
            ok = 0
            continue
        print("? " + str(mid))
        a = int(input())
        if a == 0:
            print("! " + str(mid+t))
            break
        elif a == 1:
            ok = mid+1
        else:
            ng = mid
        # 短くなる
        ok -= 1
        ng -= 1
        t += 1