# include <iostream>
# include <cstring>

using namespace std;

const int N = 510;
int g[N][N];
int dist[N];
bool st[N];

int main(){
    int n, m;
    cin >> n >> m;
    memset(g, 0x3f, sizeof g);
    while(m--){
        int x, y, z;
        cin >> x>> y >> z;
        g[x][y] = g[y][x] = min(g[x][y], z);
    }

    int res = 0;
    memset(dist, 0x3f, sizeof dist);
    dist[1] = 0;  // 1号元素
    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] == 0x3f3f3f3f){
            res = 0x3f3f3f3f;
            break;
        }
        st[t] = true;
        res += dist[t];
        for (int j=1; j<=n; j++){
            if (!st[j])
                dist[j] = min(dist[j], g[t][j]);
        }
    }
    if (res == 0x3f3f3f3f) cout << "impossible" << endl;
    else cout << res << endl;
    return 0;
}