n个社区之间的交通图用有向加权图来表示，现在要从这n个社区中选择一个社区建一所医院，问这所医院应建在哪个社区？能使所有的社区医院都比较近，能使您医院最远的社区到医院最近，或能使所有的社区到大医院的距离之和达到最小。(The traffic map between the N communities is represented by a directed weighted map. Now, a community is selected from one of the N communitie