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

using namespace std;

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

int n, m;
int p[N];

struct Edge
{
    int a, b, w;

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

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


int kruskal()
{
    //给所有边按权重大小排序
    sort(edges, edges + m);

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

    int res = 0, cnt = 0;

    //枚举每条边，因为已经排好序，所以是从小到大枚举
    for(int i = 0; i < m; i ++)
    {
        int a = edges[i].a, b = edges[i].b, w = edges[i].w;

        //找到a和b的祖宗节点，即判断a和b是否在一个连通块
        a = find(a), b = find(b);

        //如果不在就连起来
        if(a != b)
        {
            p[a] = b;
            res += w;
            cnt ++;
        }
    }

    if(cnt < n - 1) return INF;
    return res;
}

int main()
{
    scanf("%d%d", &n, &m);

    for(int i = 0; i < m; i ++)
    {
        int a, b, w;
        scanf("%d%d%d", &a, &b, &w);
        edges[i] = {a, b, w};
    }

    int t = kruskal();

    if(t == INF) puts("impossible");
    else printf("%d\n", t);

    return 0;
}