 实现下列问题的程序代码：

某石油公司计划建造一条由东向西的主输油管

道。该管道要穿过一个有n口油井的油田。从

每口油井都要有一条输油管道沿最短路径（或

南或北）与主管道相连。如果给定n口油井的

位置，即它们的x坐标和y坐标，应如何确定主

管道的最优位置，即使各油井到主管道之间的

输油管道长度总和最小的位置？-　code to achieve the following questions: a oil company plans to build a major oil pipeline from east to west. The pipeline to pass through an oil n oil wells. From each well must have a pipeline along the shortest path (or South or North) and mains connected. If the oil wells in a given position n, that is, their x coordinates and y coordinates, how to determine the optimal location of the main channel, even if the oil pipeline between the length of pipeline in the sum of the minimum position?