kruskal

#include<bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10, M = 2e5 + 10, INF = 0x3f3f3f3f;
int n, m, f[N];
struct edge{
    int f, t, l;
    edge(){}
    edge(int ff, int tt, int ll)
    {
        f = ff, t = tt, l = ll;
    }
    friend bool operator <(edge a, edge b)
    {
        return a.l < b.l;
    }
}e[M];

int get(int x)
{
    if(x != f[x]) f[x] = get(f[x]);
    return f[x];
}

int kruskal()
{
    int res = 0, cnt = 0;
    sort(e, e + m);

    for(int i = 0; i < m; i ++ )
    {
        int ff = get(e[i].f), tt = get(e[i].t), ll = e[i].l;
        if(ff != tt)
        {
            cnt ++ ;
            res += ll;
            f[ff] = tt;
        }
    }
    if(cnt == n - 1) return res;
    return INF;
}

int main()
{
    cin >> n >> m;
    for(int i = 0; i < m; i ++ )
    {
        int ff, tt, ll;
        cin >> ff >> tt >> ll;
        e[i] = edge(ff, tt, ll);
    }

    for(int i = 1; i <= n; i ++ ) f[i] = i;

    int t = kruskal();

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



    return 0;
}