说明：  给定一个n*n的地图，地图上的数为0表示不需要探索，大于0则表示需要挖掘， 现在有一位旅行商在地图的最左上方的位置，需要将所有需要拜访的地方拜访一次， 然后回到地图原点，问旅行商所走的最短路程是多少？
(Given a map of n*n, the number of zeros on the map means that no exploration is needed, and more than 0 means that mining is needed. Now there is a traveler at the top left of the map. He needs to visit all the places he needs to visit once. Then go back to the origin of the map and ask the traveler what is the shortest way to go?)