#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <deque>
#include <list>
#include <map>
#include <iostream>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <climits>
using namespace std;
const int N = 1005;
const int INF = 0x7ffffff;
int n, m;
int mat[N][N],dist1[N],dist2[N];
bool vis[N];

void Init(int dist[]) {
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            mat[i][j] = INF;
        }
    }
    fill(dist + 1, dist + 1 + n, INF);
    memset(vis, false, sizeof(vis));
}

int Find(int dist[]) {
    int pos = -1, Min = INT_MAX;
    for (int i = 1; i <= n; i++) {
        if (!vis[i]&&dist[i] < Min) {
            Min = dist[i];
            pos = i;
        }
    }
    return pos;
}


void dijkstra(int dist[]) {
    vis[1] = true;
    for (int i = 1; i <= n; i++) {
        int pos = Find(dist);
        vis[pos] = true;

        for (int j = 1; j <= n; j++) {
            if (!vis[j] && mat[pos][j] < INF && dist[pos] + mat[pos][j] < dist[j]) {
                dist[j] = dist[pos] + mat[pos][j];
            }
        }
    }
}

void rebuild_mat() {
    bool visit[N][N];
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            visit[i][j] = false;
        }
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            if (!visit[i][j] && !visit[j][i]) {
                int temp = mat[j][i];
                mat[j][i] = mat[i][j];
                mat[i][j] = temp;
                visit[i][j] = true;
                visit[j][i] = true;
            }

        }
    }
}

int main(){
    cin >> n >> m;
    Init(dist1);
    int u, v, w;
    for (int i = 1; i <= m; i++) {
        cin >> u >> v >> w;
        mat[u][v] = w;
    }
    
    for (int i = 1; i <= n; i++) {
        if (mat[1][i] < INF) {
            dist1[i] = mat[1][i];
        }
    }
    dijkstra(dist1);
    int ans = 0;
    for (int i = 2; i <= n; i++) {
        if (dist1[i] < INF) {
            ans += dist1[i];
        }
    }
    fill(dist2 + 1, dist2 + 1 + n, INF);
    memset(vis, false, sizeof(vis));
    rebuild_mat();
    for (int i = 1; i <= n; i++) {
        if (mat[1][i] < INF) {
            dist2[i] = mat[1][i];
        }
    }
    dijkstra(dist2);
    for (int i = 2; i <= n; i++) {
        if (dist2[i] < INF) {
            ans += dist2[i];
        }
    }
    cout << ans;
    return 0;
}

样例过了，但是仍旧爆0