#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;

const int N=100010,M=200010,INF=0x3f3f3f3f;

int n,m;
int p[N];
struct Edge
{
    int a,b,w;
    bool operator<(const Edge& W) const
    {
        return w<W.w;
    }
}edges[M];

int find(int x)
{
    if(x==p[x]) return x;
    return p[x]=find(p[x]);
}

int kruscal()
{
    sort(edges,edges+m);

    for(int i=1;i<=n;++i) p[i]=i;
    int res=0,cnt=0;
    for(int i=0;i<m;++i)
    {
        int a=edges[i].a,b=edges[i].b,w=edges[i].w;
        a=find(a),b=find(b);
        if(a != b)
        {
            p[a]=b;
            res+=w;
            cnt++;
        }
    }
     if(cnt<n-1) return INF;
        return res;
}

int main()
{
    cin>>n>>m;
    for(int i=0;i<m;++i)
    {
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        edges[i]={a,b,c};
    }
    int t=kruscal();
    if(t==INF) puts("impossible");
    else cout<<t<<endl;
    return 0;
}