import java.util.*;
class Edge{
    int a;  int b;    int w;
    public Edge(int a,int b,int w){
        this.a=a;   this.b=b;   this.w=w;
    }
}
public class Main {
    static int N = 100010;
    static int n,m;
    static int[] p = new int[N];
    static int find(int x){
        if(p[x]!=x) p[x]=find(p[x]);
        return p[x];
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        m = sc.nextInt();
        Edge[] edge = new Edge[m];
        for(int i=0;i<m;i++){
            int a = sc.nextInt();   int b = sc.nextInt();   int w = sc.nextInt();
            Edge e = new Edge(a,b,w);
            edge[i]=e;
        }
        Arrays.sort(edge, new Comparator<Edge>() {
            @Override
            public int compare(Edge o1, Edge o2) {
                if(o1.w<o2.w)   return -1;
                else if(o1.w>o2.w)  return 1;
                else return 0;
            }
        });
        for(int i=1;i<n;i++)    p[i]=i;
        int res=0,cnt=0;
        for(int i=0;i<m;i++){
            int a = edge[i].a;  int b = edge[i].b;  int w = edge[i].w;
            a = find(a);b=find(b);
            if(a!=b){
                p[a]=b; res+=w; cnt++;
            }
        }
        if(cnt<n-1) System.out.println("impossible");
        else System.out.println(res);
    }
}