第一个5分，后面全WA

#include <iostream>
#include <vector>
#include <queue>
#include <utility>
#include <cstring>
using namespace std;

const int MAXN = 1000006;
const int INF = 0x3f3f3f3f;

struct Edge {
    int to, cost;
};

vector<Edge> graph[MAXN];
bool visited[MAXN];
int dist[MAXN];

int prim(int n) {
    int totalCost = 0;
    memset(visited, false, sizeof(visited));
    fill(dist, dist + n + 1, INF);

    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
    pq.push(make_pair(0, 1)); // 从1号国家开始

    while (!pq.empty()) {
        int u = pq.top().second;
        int d = pq.top().first;
        pq.pop();

        if (visited[u]) continue;
        visited[u] = true;
        totalCost += d;

        for (const Edge& e : graph[u]) {
            int v = e.to;
            int cost = e.cost;
            if (!visited[v] && cost < dist[v]) {
                dist[v] = cost;
                pq.push(make_pair(cost, v));
            }
        }
    }

    return totalCost;
}

int main() {
    int n;
    cin >> n;
    for (int i = 1; i < n; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        graph[a].push_back({b, c});
        graph[b].push_back({a, c});
    }

    int totalCost = prim(n);
    cout << totalCost << endl;

    return 0;
}