import java.io.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

class Main {

    static class Edege implements Comparable<Edege> {
        int start, end, weight;

        public Edege(int start, int end, int weight) {
            this.start = start;
            this.end = end;
            this.weight = weight;
        }

        @Override
        public int compareTo(Edege o) {
            return this.weight - o.weight;
        }
    }

    //边数组存放所有边
    static int n, m;
    static int idx;
    static List<Edege> edeges = new ArrayList<>();

    //并查集存放已纳入生成树结点
    static int[] p = new int[100010];
    //当前集合的边权和
    static int[] sum = new int[100010];
    //当前集合的点数量
    static int[] cnt = new int[100010];

    static void insert(int a, int b, int w) {
        //忽略自环
        if (a == b) return;
        edeges.add(new Edege(a, b, w));
    }

    //注意并查集写法
    static int find(int x) {
        if (p[x] != x) {
            p[x] = find(p[x]);
        }
        return p[x];
    }

    static boolean kruskal() {
        Collections.sort(edeges);
        for (int i = 0; i < edeges.size(); i++) {
            Edege edege = edeges.get(i);
            //注意并查集用法
            int a = find(edege.start);
            int b = find(edege.end);
            int w = edege.weight;
            if ( a!= b) {
                cnt[b] += cnt[a];
                p[a] = b;
                sum[b] += (sum[a] + w);
                if (cnt[b] == n) return true;
            }
        }
        return false;
    }

    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 = 1; i <= n; i++) {
            p[i] = i;
            cnt[i] = 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 w = Integer.parseInt(strs[2]);
            insert(a, b, w);
        }

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

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

        if (kruskal()) out.write(sum[find(1)] + "");
        else out.write("impossible");

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