#include <bits/stdc++.h>
using namespace std;

#define be(v) (v).begin(), (v).end()
#define sz(v) v.size()
#define pb push_back
#define mk make_pair
#define oo 100010
#define s second
#define f first

int p,r,a,b,c,visi[1000],pai[100];
vector<pair<int,pair<int,int> > > vv;
vector<vector<int> > g;

void dfs(int u){
    visi[u] = 1;
    for(int k=0;k<g[u].size();k++){
        if(visi[g[u][k]] == 0){
            visi[g[u][k]] = 1;
            dfs(g[u][k]);
        }
    }
}

int find(int u){
    return pai[u] == u ? u:pai[u] = find(pai[u]);
}

int kruskal(){

    int fa,fb,soma = 0;
    sort(vv.begin(),vv.end());

    for(int i=0;i<vv.size();i++){

        fa = find(vv[i].s.f);
        fb = find(vv[i].s.s);

        if(fa != fb){
            pai[fb] = fa;
            soma += vv[i].f;
        }
    }

    return soma;
}


int main() {

    while(cin >> p >> r){

        vv.clear();
        g.assign(p+10,vector<int>());
        memset(visi,0,sizeof visi);
        for(int k=1;k<p+1;k++) pai[k] = k;

        for(int k=0;k<r;k++){
            cin >> a >> b >> c;
            vv.pb(mk(c,mk(a,b)));
            g[a].pb(b);
            g[b].pb(a);
        }

        int cont = 0;
        for(int k=1;k<p+1;k++){
            if(visi[k] == 0){
                dfs(k);
                cont++;
            }
        }

        if(cont == 1) cout << kruskal() << endl;
        else cout << "impossivel\n";
    }
}