#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <queue>
using namespace std;

const int N = 1e5 + 10;

struct edge {
    int u, v, w;
    bool operator<(const edge &t) const {
        return w < t.w;
    }
}e[N * 2];
int d[N];
bool vis[N];
int fa[N];
int ans, cnt;
int n, m;

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

bool kruskal() {
    for (int i = 1; i <= n; i++)
        fa[i] = i;
    sort(e, e + m);
    for (int i = 0; i < m; i++) {
        int x = find(e[i].u);
        int y = find(e[i].v);
        if (x != y) {
            ans += e[i].w;
            cnt++;
            fa[x] = y;
        }
    }
    return cnt == n - 1;
}



int main()
{
    scanf("%d%d", &n, &m);
    int u, v, w;
    for (int i = 0; i <m; i++) {
        scanf("%d%d%d", &u, &v, &w);
        e[i] = {u, v, w} ;
        e[i] = {v, u, w};
    }
    if (kruskal())
        cout << ans << endl;
    else
        cout << "impossible" << endl;
    return 0;
}