14.// prim最小生成树

#include<cstring>
#include<iostream>
#include<algorithm>

using namespace std;

const int N = 510, INF = 0x3f3f3f3f;

int n, m;
int g[N][N];
int dist[N];
bool st[N];  //与dijkstra的不同

int prim() {
    memset(dist, 0x3f, sizeof dist); // dist表示到集合的距离

    int res = 0;
    for(int i = 0; i < n; i ++) {
        int t = -1;
        for(int j = 1; j <= n; j ++) 
            if(!st[j] && (t == -1 || dist[t] > dist[j]))
                t = j;

        if(i && dist[t] == INF) return INF;
        if(i) res += dist[t]; // y.错， 在更新前就相加

        for(int j = 1; j <= n; j ++) dist[j] = min(dist[j], g[t][j]); // 和dijkstra的不同，这里不是没有＋dist[t]

        st[t] = true;
    }
    return res;
}

int main() {
    cin >> n >> m;
    memset(g, 0x3f, sizeof g);

    while(m --) {
        int a, b, c;
        cin >> a >> b >> c;
        g[a][b] = g[b][a] = min(g[a][b], c);
    }

    int t = prim();

    if(t == INF) puts("impossible");
    else cout << t << endl;

    return 0;
}