1 #include <stdio.h>
 2 #include <algorithm>
 3 using namespace std;
 4 int father[1010] ;
 5 
 6 struct rode
 7 {
 8     int a, b ,c;
 9 };
10 rode num[10010];
11 
12 bool cmp(rode a, rode b)
13 {
14     return a.c < b.c ;
15 }
16 
17 int find(int a)
18 {
19     while(a != father[a])
20     a = father[a];
21     return a;
22 }
23 
24 void mercy(int a, int b)
25 {
26     int q = find(a);
27     int p = find(b);
28     if(q != p)
29     father[q] = p;
30         
31 }
32 
33 int main()
34 {
35     int i, n, m;
36     while(~scanf("%d %d", &n, &m))
37     {
38         for(i=0; i<n; i++)
39         father[i] = i;
40         for(i=0; i<m; i++)
41         scanf("%d %d %d",&num[i].a, &num[i].b, &num[i].c);
42         sort(num, num+m, cmp);
43         int total = 0;
44         for(i=0; i<m; i++)
45         {
46             //mercy(num[i].a, num[i].b);
47             if(find(num[i].a) == find(num[i].b))
48             continue;
49             else
50             {
51                 //printf("1\n");
52                 total += num[i].c;
53                 mercy(num[i].a, num[i].b) ;
54             }    
55         }
56         int ac = 0;
57         for(i=0; i<n; i++)
58         {
59             if(father[i] == i)
60             ac++;
61         }
62         if(ac == 1)
63         printf("%d\n\n", total);
64         else
65         printf("impossible\n\n");
66     }
67 }