说明：  省政府“畅通工程”的目标是使全省任何两个村庄间都可以实现公路交通（但不一定有直接的公路相连，只要能间接通过公路可达即可）。经过调查评估，得到的统计表中列出了有可能建设公路的若干条道路的成本。现请你编写程序，计算出全省畅通需要的最低成本。
(The provincial government open project the goal is to make the province between any two villages can realize road traffic (but not necessarily directly connected to the highway, as long as they can reach by road can be indirect). After investigation, assessment, have been listed in the tables may be building a number of highway road costs. Now invite you to write programs to calculate the flow needs of the province the lowest cost.)