After reaching the last ordered path, the first node of {TAIL ~ each path} in {HEAD ~ the group} is removed 
After reaching the last ordered path , the first node of { TAIL ~ each path } in { HEAD ~ the group } is removed
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH