#include <iostream>
#include <vector>
#include <queue>


using namespace std;



int main(){
    int n,m;
    cin>>n>>m;
    vector<vector<pair<int, int>>> adj(n+1);
    for(int i=0;i<m;i++){
        int u,v,p;
        cin>>u>>v>>p;
        adj[u].push_back({v, p});
    }
    int st, fn;
    cin>>st>>fn;
    priority_queue<pair<int,int>, vector<pair<int,int>>, greater<pair<int,int>>> pq;
    dist[N+1] = {INT_MAX};
    pq.push({0, st});
    dist[st] = 0;
    while(!pq.empty()){
        auto [d, node] = pq.top();
        pq.pop();
        if(d > dist[node]) continue;
        for(auto [nei, weight]: adj[node]){
            if(dist[node] + weight < dist[nei]){
                dist[nei] = dist[node] + weight;
                pq.push({dist[nei], nei});
            }
        }
    }
    if(dist[fn] == INT_MAX){
        cout<<-1<<endl;
    } else {
        cout<<dist[fn]<<endl;
    }

    return 0;
}