给定一个N*N 的方形网格，设其左上角为起点◎，坐标为（1，1），X 轴向右为正，Y 轴向下为正，每个方格边长为1。一辆汽车从起点◎出发驶向右下角终点▲，其坐标为（N， N）。在若干个网格交叉点处，设置了油库，可供汽车在行驶途中加油。汽车在行驶过程中应遵守如下规则：





　　求汽车从起点出发到达终点的一条所付费用最少的行驶路线。-Given an N* N square grid, set the upper left corner as a starting point ◎, coordinates (1,1), X-axis to the right is positive, Y axis under positive side of each box is 1. A car starting from the starting point towards the bottom right corner of the end ◎ ▲, the coordinates (N, N). In a number of grid intersection points, set the oil tanks, fuel for the car is moving his way. The car is moving process should observe the following rules: find cars starting from the starting point to reach the end of a driving route with the least paid.