第一行包括两个数字 N（村子数量 2 < N < 1,000）M(可以修的道路数量 1 < M <

20,000)

在下面的 M 行中，每行有 3 个数字 ABC，表示 AB 两个村庄之间的道路长度是 C。

条件：这条路尽可能的长并且把所有村庄连在一起，这条路不存在环-The first line contains two numbers N (village number 2 <　 N <　 1,000) M (the number of road can repair 1 <　 M <　 20,000) in the following M lines, each line has three digital ABC, showing length of the road between the two villages is AB C. Conditions: this road as long as possible and put together all the villages, there is no ring road