#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;
    node () {}
    node(int _idx, int _sh) {
        idx = _idx;
        shorest_path_till_idx = _sh;
    }
    // < a < b
    bool operator < (const node &t) const {
        return shorest_path_till_idx > t.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
    priority_queue<node> pq;
    pq.push(node(S, 0));
    while(!pq.empty()) {
        node current = pq.top();
        pq.pop();
        if(visited[current.idx]) {
            continue;
        }
        visited[current.idx] = true;
        if(current.idx == E) {
            return current.shorest_path_till_idx;
        }
        for(int i = 0; i < (int) graph[current.idx].size(); ++i) {
            int neighbour = graph[current.idx][i].first;
            int neighbour_weight = graph[current.idx][i].second;
            if(!visited[neighbour] and neighbour_weight + current.shorest_path_till_idx < dist[neighbour]) {
                dist[neighbour] = current.shorest_path_till_idx + neighbour_weight;
                pq.push(node(neighbour, dist[neighbour]));

            }
        }
    }

    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;
}
/*
 tp:
  5 6
  1 2 5
  2 3 6
  3 4 8
  1 5 2
  3 5 3
  4 2 9
  2 5

 */