a searching unit to search the route information of the respective links connected via {TAIL ~ the respective node} corresponding to {HEAD ~ the starting position}; and 
a searching unit to search the route information of the respective links connected via { TAIL ~ the respective node } corresponding to { HEAD ~ the starting position } ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH