/*
 * @Author: Wangshuo Tau
 * @Date: 2024-12-12 10:02:59
 * @LastEditTime: 2024-12-12 10:09:58
 * @Description: 
 */
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>

using namespace std;

const int N = 510, INF = 0x3f3f3f3f;
struct edge {
    int v, w;
};
vector<edge> e[N];
int d[N];
bool vis[N];
int ans, cnt;
int n, m;

bool prim(int s) {
    for (int i = 0; i <= n; i++) {
        d[i] = INF;
    }
    d[s] = 0;

    for (int i = 1; i <= n; i++) {
        int u = 0;
        for (int j = 1; j <= n; j++) {
            if (!vis[j] && d[j] < d[u]) 
                u = j;
        }
        if (d[u] == INF) return false;
        vis[u] = 1;
        ans += d[u];
        cnt++;
        for (auto ed : e[u]) {
            int v = ed.v, w = ed.w;
            if (d[v] > w) {
                d[v] = w;
            }
        }
    }
    return cnt == n;
}

int main() {
    scanf("%d%d", &n, &m);
    int u, v, w;
    while (m--) {
        scanf("%d%d%d", &u, &v, &w);
        e[u].push_back({v, w});
        e[v].push_back({u, w});
    }
    if (prim(1)) 
        cout << ans << endl;
    else 
        cout << "impossible" << endl;
    return 0;
}