import java.io.*;
import java.util.Arrays;

class Main {
    static final int INF = 0x3fffffff;

    //稠密图，邻接矩阵存放
    static int n, m;
    static int[][] g = new int[550][550];
    //dist数组存放结点到生成树集合的距离
    static int[] dist = new int[550];
    //存放是否已加入生成树中
    static boolean[] flag = new boolean[550];
    //权重之和
    static int sum;
    //点数之和
    static int cnt;

    static {
        for (int i = 0; i < 520; i++) {
            Arrays.fill(g[i], INF);
            g[i][i] = 0;
        }
        Arrays.fill(dist, INF);
    }

    static void insert(int a, int b, int c) {
        //忽略自环
        if (a == b) return;
        g[a][b] = g[b][a] = Math.min(g[a][b], c);
    }

    static boolean prime() {
        //从第一个顶点开始找
        dist[1] = 0;
        for (int i = 1; i <= n; i++) {
            int t = 0;
            for (int j = 1; j <= n; j++)
                if (!flag[j] && dist[j]<dist[t]) t = j;
            if (t == 0) break;
            flag[t] = true;
            sum += dist[t];
            cnt++;
            if (cnt == n) return true;
            //注意，更新距离时使用t点到j点与原j点距离对比
            for (int j = 1; j <= n; j++) if (!flag[j]) dist[j] = Math.min(g[t][j], dist[j]);
        }
        return cnt == n;
    }

    public static void main(String[] args) throws IOException {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader in = new BufferedReader(isr);
        String[] strs = in.readLine().split(" ");
        n = Integer.parseInt(strs[0]);
        m = Integer.parseInt(strs[1]);
        for (int i = 0; i < m; i++) {
            strs = in.readLine().split(" ");
            int a = Integer.parseInt(strs[0]);
            int b = Integer.parseInt(strs[1]);
            int c = Integer.parseInt(strs[2]);
            insert(a, b, c);
        }

        in.close();
        isr.close();

        OutputStreamWriter osw = new OutputStreamWriter(System.out);
        BufferedWriter out = new BufferedWriter(osw);

        if (prime()) out.write(sum + "");
        else out.write("impossible");

        out.flush();
        out.close();
        osw.close();
    }
}