#include <bits/stdc++.h>

using namespace std;

const int INF = 0x3f3f3f3f;
int n, m; // n条顶点,m条边
int res;  // 最小生成树的权值和
int cnt;  // 组成最小生成树的结点数
// Kruskal用到的结构体
const int N = 100010, M = N << 1;
struct Node {
    int a, b, w;
    bool const operator<(const Node &ed) const {
        return w < ed.w;
    }
} edge[M];
// 并查集
int p[N];
int find(int x) {
    if (p[x] != x) p[x] = find(p[x]);
    return p[x];
}
// Kruskal算法
int kruskal() {
    sort(edge, edge + m);
    for (int i = 1; i <= n; i++) p[i] = i;
    for (int i = 0; i < m; i++) {
        int a = edge[i].a, b = edge[i].b, w = edge[i].w;
        a = find(a), b = find(b);
        if (a != b)
            p[a] = b, res += w, cnt++; // cnt是指已经连接上边的数量
    }
    if (cnt < n - 1) return INF;
    return res;
}

int main() {
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        edge[i] = {a, b, c};
    }
    int t = kruskal();
    if (t == INF)
        puts("impossible");
    else
        printf("%d\n", t);
    return 0;
}