def do_tre(thoi_gian_xu_ly, moc_den=None):
    ket_thuc = 0
    do_tre_ms = []
    for i, xu_ly in enumerate(thoi_gian_xu_ly):
        den = ket_thuc if moc_den is None else moc_den[i]
        ket_thuc = max(den, ket_thuc) + xu_ly
        do_tre_ms.append(ket_thuc - den)
    return do_tre_ms

xu_ly = [500, 20, 20, 20]
tai_mo = do_tre(xu_ly, [0, 100, 200, 300])
tai_dong = do_tre(xu_ly)
assert tai_mo == [500, 420, 340, 260]
assert tai_dong == [500, 20, 20, 20]
print("Tải mở", tai_mo, "| Tải đóng", tai_dong)