def main():
    left = -1;
    right = 10 ** 9 + 1
    while right - left > 1:
        mid = left + (right - left) // 2
        print('?', mid)
        if int(input()) == 1:
            left = mid
        else:
            right = mid
    print('!', left)


if __name__ == "__main__":
    main()