/**

图论之最短路径Dijkstra算法

*/

#include<string.h>

#include<stdio.h>

#include<vector>

#include<queue>

using namespace std;

const int MAXN = 200;

const int INF = 0x7fffffff;

struct Edge

{

    int to ;

    int length;

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

};

vector<Edge> graph[MAXN];

int dis[MAXN];

bool visit[MAXN];

void Dijkstra (int start, int n)

{

    memset(visit, false, sizeof(visit));

    fill(dis, dis+n, INF);

    dis[start] = 0;

    for(int i=0;i<n;i++)

    {

        int u=-1;

        for(int j=0;j<n;j++)

        {

            if(visit[j]) continue;

            if(u == -1 || dis[j]<dis[u])

            {

                u = j;

            }

        }

        for(int j=0;j<graph[u].size();j++)

        {

            int v = graph[u][j].to;

            int d = graph[u][j].length;

            if(dis[u] + d < dis[v])

            {

                dis[v] = dis[u] + d;

            }

        }

        visit[u] = true;

    }

    return ;

}

int main ()

{

    int n,m;

    scanf("%d%d",&n,&m);

    memset(graph, 0, sizeof(graph));

    while(m--)

    {

        int from, to, length;

        scanf("%d%d%d", &from, &to, &length);

        graph[from].push_back(Edge(to, length));

        graph[to].push_back(Edge(from, length));

    }

    int start, terminal;

    scanf("%d%d",&start, &terminal);

    Dijkstra(start, n);

    if(dis[terminal] == INF)

    {

        dis[terminal] = -1;

    }

    printf("%d\n",dis[terminal]);

    return 0;

}

/**

3 3

0 1 1

0 2 3

1 2 1

0 2

输出2

3 1

0 1 1

1 2

输出-1

*/