#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
int n,m;
const int N=505,M=200005,INF=0x3f3f3f3f;
int g[N][N];
int dist[N];//点到集合的距离
bool st[N];
int prim(){
    int res=0;
    memset(dist,0x3f,sizeof dist);
    for(int i=0;i<n;i++){
        int t=-1;
        for(int j=1;j<=n;j++){
            if(!st[j]&&(t==-1||dist[j]<dist[t])){
                t=j;
            }
        }
        if(i&&dist[t]==INF) return INF;//这句来判断无解情况
        if(i) res+=dist[t];
        st[t]=true;
        for(int j=1;j<=n;j++){
            dist[j]=min(dist[j],g[t][j]);
        }
    }
    return res;
}
int main()
{
    cin>>n>>m;
    memset(g,0x3f,sizeof g);
    for(int i=0;i<m;i++){
        int a,b,c;
        cin>>a>>b>>c;
        g[a][b]=min(g[a][b],c);
        g[b][a]=g[a][b];
    }
    int ans=prim();
    if(ans==INF) cout<<"impossible";
    else
    cout<<ans<<endl;
    //cout << "Hello world!" << endl;
    return 0;
}