参考答案：

#include<iostream>
#include<algorithm>

using namespace std;

const int N = 100010, M = 2 * N, INF = 0x3f3f3f3f;
int p[N];
int n, m;

struct Edge
{
    int a, b, c;
    bool operator<(const Edge& W) const
    {
        return c < W.c;
    }
}edge[M];

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

int kruskal()
{
    sort(edge + 1, edge + m + 1);
    int res = 0, t = 0;

    for (int i = 1; i <= m; ++i)
    {
        int a = edge[i].a, b = edge[i].b, c = edge[i].c;
        a = find(a), b = find(b);
        if (a != b)
        {
            p[a] = b;
            res += c;
            t++;
        }
    }

    if (t < n - 1) return INF;
    return res;
}
int main()
{
    cin >> n >> m;

    for (int i = 1; i <= n; ++i) p[i] = i;
    for (int i = 1; i <= m; ++i)
    {
        cin >> edge[i].a >> edge[i].b >> edge[i].c;
    }

    int t = kruskal();

    if (t == INF) cout << "Not exist" << endl;
    else cout << t << endl;

    return 0;
}