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1853：Cyclic Tour

题目描述
There are N cities in our country, and M one-way roads connecting them. Now Little Tom wants to make several cyclic tours, which satisfy that, each cycle contain at least two cities, and each city belongs to one cycle exactly. Tom wants the total length of all the tours minimum, but he is too lazy to calculate. Can you help him?
输入解释
There are several test cases in the input. You should process to the end of file (EOF).
The first line of each test case contains two integers N (N ≤ 100) and M, indicating the number of cities and the number of roads. The M lines followed, each of them contains three numbers A, B, and C, indicating that there is a road from city A to city B, whose length is C. (1 ≤ A,B ≤ N, A ≠ B, 1 ≤ C ≤ 1000).
输出解释
Output one number for each test case, indicating the minimum length of all the tours. If there are no such tours, output -1.
输入样例 
6 9
1 2 5
2 3 5
3 1 10
3 4 12
4 1 8
4 6 11
5 4 7
5 6 9
6 5 4
6 5
1 2 1
2 3 1
3 4 1
4 5 1
5 6 1
输出样例 
42
-1
提示
 In the first sample, there are two cycles, (1->2->3->1) and (6->5->4->6) whose length is 20 + 22 = 42.
来自杭电HDUOJ的附加信息
Author RoBa@TJU
Recommend lcy
该题目是Virtual Judge题目，来自 杭电HDUOJ
题目来源 HDU 2007 Programming Contest - Final
源链接： HDU-1853
最后修改于 2020-10-25T22:48:18+00:00 由爬虫自动更新
共提交 0 次
通过率 --%
时间上限 内存上限
1000/1000MS(Java/Others) 32768/65535K(Java/Others)