#include <iostream>
#include <algorithm>
#include <cstdio>
using namespace std;
const int N = 2 * 1E5 + 10;
struct node{
    int a, b, w;
    bool operator < (const node & other) const{
        return w < other.w;
    }
};
node edge[N];
int n, m;
void read(){
    cin >> n >> m;
    for(int i = 0; i < m; i ++ ){
        scanf("%d%d%d", &edge[i].a, &edge[i].b, &edge[i].w);
    }
}
int parent[N];
int find(int t){
    if(parent[t] != t) parent[t] = find(parent[t]);
    return parent[t];
}
void kruskal(){
    for(int i = 0; i < n; i ++ )    parent[i] = i;
    sort(edge, edge + m);
    int a, b, w;
    int res = 0, cnt = 0;
    for(int i = 0; i < m; i ++ ){
        a = edge[i].a;
        b = edge[i].b;
        w = edge[i].w;
        a = find(a), b = find(b);
        if(a != b){
            parent[a] = b;
            res += w;
            cnt ++ ;
        }  
    }
    if(cnt == n - 1)    cout << res << endl;
    else    cout << "impossible" << endl;
}
int main(){
    read();
    kruskal();
    return 0;
}