57分，WA在测试点16,19,20上。求调。

#include <bits/stdc++.h>
using namespace std;
#define N 20005

long long n, m, s, t;
long long x, y, z;
long long d[N], v[N];
long long minn = 0x3f3f3f3f3f3f3f3f3f;
struct Node {
    int to;
    long long w, st;
    bool operator<(const Node &a) const {
        return w > a.w || (w == a.w && st > a.st);
    }
};
vector<Node> g[N];

priority_queue<Node> q;

void dijkstra() {
    while (!q.empty()) {
        Node cur = q.top();
        q.pop();
        if (v[cur.to] <= cur.st) continue;
        v[cur.to] = cur.st;

        for (int j = 0; j < g[cur.to].size(); j++) {
            Node next = g[cur.to][j];
            if (v[next.to] >= cur.st + 1) {
                int ns = 0, nt = cur.st + 1;
                if (d[cur.to] + next.w / cur.st < d[next.to]) {
                    d[next.to] = d[cur.to] + next.w / cur.st;
                }

                while (nt <= next.w) {
                    q.push(Node{next.to, d[next.to] + ns, nt});
                    ns += next.w / nt;
                    nt += 1;
                    ns += next.w / nt;
                    nt += 1;
                }
                minn = min(minn, d[next.to] + ns);
            }
        }
    }
}

int main() {
    cin >> n >> m >> s >> t;
    for (int i = 1; i <= m; i++) {
        cin >> x >> y >> z;
        g[x].push_back(Node{y, z});
        g[y].push_back(Node{x, z});
    }
    for (int i = 1; i <= n; i++) d[i] = v[i] = 0x3f3f3f3f3f3f3f3f3f;

    d[t] = 0;
    q.push(Node{t, 0, 1});
    dijkstra();
    cout << min(d[s], minn) ;
    return 0;
}