#include<iostream>
#include<algorithm>
#include<cstring>

using namespace std;

const int N = 100010, M = 200010, INF = 0x3f3f3f3f;

int n, m;
int p[N];

struct Edges{
    int a, b, w;

    bool operator< (const Edges &e) const 
    {
        return w < e.w;
    }
}edges[M];

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

int kruskal()
{
    // 1. 对边权从小到大排序
    sort(edges, edges + m);

    for (int i = 1; i <= n; i ++ ) p[i] = i;  // 初始化并查集

    int res = 0, cnt = 0;  // cnt 用来统计边数
    // 2. 从小到大枚举每条边，边连上，长度加上，计数+1
    for (int i = 0; i < m ; i ++ ) 
    {
        int a = edges[i].a, b = edges[i].b, w = edges[i].w;

        a = find(a), b = find(b);

        if (a != b)
        {
            p[a] = b;
            res += w;
            cnt ++ ;
        }
    }

    if (cnt < n - 1) return INF;  // 连通图的边数 = 点数 - 1 
    else return res;
}

int main()
{
    cin >> n >> m;
    for (int i = 0; i < m ; i ++ )
    {
        int a, b, w;
        cin >> a >> b >> w;

        edges[i] = {a, b, w};
    }

    int t = kruskal();

    if (t == INF) puts("impossible");
    else cout << t << endl;

    return 0;
}