/*
-------------------------------------------------
   Author:       wry
   date:         2022/2/26 21:56
   Description:  Dijkstra
-------------------------------------------------
*/

#include <bits/stdc++.h>

using namespace std;

const int MAXN = 200;

struct Edge {
    int to;
    int length;
    Edge(int t,int l):to(t),length(l){}
};

struct Point {
    int id;
    int distance;
    Point(int n,int d):number(n),distance(d){}
    bool operator< (Point p) const{
        return distance>p.distance;     //距离越小，优先级越高
    }
};

vector<Edge> graph[MAXN];
int dis[MAXN];   //表示起点到此测试点的最短距离

void Disjkstra(int start,int n) {
    fill(dis,dis+n,INT_MAX);
    dis[start] = 0;
    priority_queue<Point> myPriorityQueue;
    myPriorityQueue.push(Point(start,dis[start]));    //存入第一个点，即它自己
    while (!myPriorityQueue.empty()) {
        int p = myPriorityQueue.top().id;
        myPriorityQueue.pop();
        for (int i=0;i<graph[p].size();i++) {    //p _l_> q
            int q = graph[p][i].to;
            int l = graph[p][i].length;
            if (dis[p]+l<dis[q]) {    //看是直接到q近还是经过p中转近
                dis[q] = dis[p]+l;
                myPriorityQueue.push(Point(q,dis[q]));
            }
        }
    }
}

int main() {
    int n,m;
    while (cin>>n>>m) {
        memset(graph,0,sizeof(graph));    //初始化结构体的向量
        while (m--) {
            int from,to,length;
            cin >> from >> to >> length;
            //Dijkstra应用于无向图
            graph[from].push_back(Edge(to,length));
            graph[to].push_back(Edge(from,length));
        }
        int start,end;
        cin >> start >> end;
        Disjkstra(start,n);
        if (dis[end]==INT_MAX) {
            dis[end] = -1;
        }
    }
    return 0;
}