On basis of the distribution graph, {TAIL ~ the shortest paths} from the distribution node to {HEAD ~ each} of the other nodes are calculated 
On basis of the distribution graph , { TAIL ~ the shortest paths } from the distribution node to { HEAD ~ each } of the other nodes are calculated
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH