#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
const int INF = 2e9 + 10;
vector<pair<int, int>> graph[maxn]; // graph[i].first - node, graph[i].second - weight
int n, m;
struct node {
    int idx, shorest_path_till_idx;

};
int dijkstra(int S, int E) {
    vector<bool> visited(n + 1, false);
    vector<int> dist(n + 1, INF);
    dist[S] = 0; // shortest distance from source to source = 0
    return -1;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin >> n >> m;
    for(int i = 0; i < m; ++i) {
        int a, b, c;
        cin >> a >> b >> c;
        graph[a].push_back(make_pair(b, c));
        graph[b].push_back(make_pair(a, c));
        //undirected graph
    }
    int start, end;
    cin >> start >> end;
    cout << dijkstra(start, end) << endl;
    return 0;
}