Therefore, even if a main course box is out of order {TAIL ~ the data} remains in {HEAD ~ the sub course box} 
Therefore , even if a main course box is out of order { TAIL ~ the data } remains in { HEAD ~ the sub course box }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD