oa->first_ttime[i] = min(oa->first_ttime[i], ob->first_ttime[i]);
oa->last_ttime[i] = max(oa->last_ttime[i], ob->last_ttime[i]);
merge_bs(&oa->bs[i], &oa->nr_bs[i], ob->bs[i], ob->nr_bs[i]);
oa->first_ttime[i] = min(oa->first_ttime[i], ob->first_ttime[i]);
oa->last_ttime[i] = max(oa->last_ttime[i], ob->last_ttime[i]);
merge_bs(&oa->bs[i], &oa->nr_bs[i], ob->bs[i], ob->nr_bs[i]);