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#include <iostream>
#include <limits>
#include <vector>
#include <queue>
using std::vector;
using std::priority_queue;
int distance(vector<vector<int> > &adj, vector<vector<int> > &cost, int s, int t)
{
vector<int> dists(adj.size(), std::numeric_limits<int>::max());
std::priority_queue<int, std::vector<int>, std::greater<int>> pq;
dists[s] = 0;
pq.push(s);
while(!pq.empty()) {
int n = pq.top();
int dist = dists[n];
/* std::cout << " pop: " << n + 1 << " : " << dist << std::endl; */
pq.pop();
for (int i = 0; i < adj[n].size(); i++) {
int a = adj[n][i];
int nd = dist + cost[n][i];
if (dists[a] > nd) {
dists[a] = nd;
/* std::cout << " push: " << a + 1 << " : " << dists[a].first << std::endl; */
pq.push(a);
}
}
}
return (dists[t] == std::numeric_limits<int>::max() ? -1 : dists[t]);
}
int main() {
int n, m;
std::cin >> n >> m;
vector<vector<int> > adj(n, vector<int>());
vector<vector<int> > cost(n, vector<int>());
for (int i = 0; i < m; i++) {
int x, y, w;
std::cin >> x >> y >> w;
adj[x - 1].push_back(y - 1);
cost[x - 1].push_back(w);
}
int s, t;
std::cin >> s >> t;
s--, t--;
std::cout << distance(adj, cost, s, t) << '\n';
}
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