include[HTML_REMOVED]

#include<cstring>
#include<algorithm>

using namespace std;

const int N = 510, M = 100010, INF = 0x3f3f3f3f;
int n,m;
int g[N][N];
int dist[N];
bool st[N];

int prim(){
    memset(dist,0x3f,sizeof dist);
    dist[1] = 0;
    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(dist[t] == INF)  return INF;
        st[t] = true;
        res += dist[t];
        for(int j = 1; j<=n ;j++){
            dist[j] = min(dist[j], g[t][j]);
        }

    }
    return res;

}

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

    while(m--){
        int a,b,c;
        cin>>a>>b>>c;
        g[a][b] = g[b][a] = min(g[a][b], c);
    }
    int res = prim();
    if(res == INF)  puts("impossible");
    else    cout<<res<<endl;

    return 0;
}