#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';
}