if __name__ == "__main__":
    center_num = int(1000000000 / 2)
    num_range = int(1000000000 / 2)

    while not num_range == 1:
        print("? {}".format(center_num), flush=True)
        res = int(input()) == 1
        if res:
            center_num = center_num + int(num_range / 2)
        else:
            center_num = center_num - int(num_range / 2)
        num_range = int((num_range + 1) / 2)

    print("? {}".format(center_num), flush=True)
    res = int(input()) == 1
    if res:
        print("? {}".format(center_num + 1), flush=True)
        res = int(input()) == 1
        if res:
            center_num += 1
    else:
        center_num -= 1
    print("! {}".format(center_num), flush=True)