static long long ustime(void) {
    struct timeval tv;
    long long ust;

    gettimeofday(&tv, NULL);
    ust = ((long long)tv.tv_sec) * 1000000;
    ust += tv.tv_usec;
    return ust;
}
static long long ustime(void) {
    struct timeval tv;
    long long ust;

    gettimeofday(&tv, NULL);
    ust = ((long long)tv.tv_sec) * 1000000;
    ust += tv.tv_usec;
    return ust;
}