在一个就是火车站旁有一座桥，其桥面可以绕河中心的桥墩水平旋转。该车站职工发现桥的长度最多只能容纳两节车厢，如果将桥旋转180度，则可以把相邻两节车厢的位置交换，用这种方法可以重新排列车厢的顺序。于是他就负责用这座桥将进站的车厢按车厢号从小到大排列。在他退休后，火车站决定将这一工作自动化，其中一项重要的工作是编一个程序，输入初始的车厢顺序，计算最少用多少步就能将车厢排好序。-The train station next to a bridge, the bridge piers for river levels around the rotation. The station staff found that the length of the bridge can only accommodate two cars, if the bridge rotated 180 degrees, you can put two cars adjacent to the location of the exchange, this way you can rearrange the order of cars. So he takes responsibility for the bridge to stop the car by car number from small to large order. After his retirement, the railway station decided to automate this work, one important task is to compile a program, enter the initial order of the cars, calculate how many steps will be able to at least train with sorted.