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

const int N=510,INF=0x3f3f3f3f;

int n,m;
int g[N][N];
int dist[N];
bool st[N];

int prim()
{
    memset(dist,0x3f,sizeof dist);
    int res=0;
    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;
        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);
    while(m--)
    {
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        g[a][b]=g[b][a]=min(g[a][b],c);
    }
    int t=prim();
    if(t==INF) puts("impossible");
    else cout<<t<<endl;
    return 0;
}