#include<iostream>

 #include<cstring>

 #include<cstdio>

 #include<queue>

 using namespace std;

 const int maxn = ;

 vector<pair<int, int> > E[maxn];

 int d[maxn], inq[maxn];

 int n, m,s,t;

 void SPFA(int s)

 {

     queue<int> Q;

     Q.push(s); d[s] = , inq[s] = ;

     while (!Q.empty())

     {

         int now = Q.front(); Q.pop();

         inq[now] = ;

         for (int i = ; i < E[now].size(); i++) {

             int v = E[now][i].first;

             if (d[v] > d[now] + E[now][i].second)

             {

                 d[v] = d[now] + E[now][i].second;

                 if (inq[v] == ) continue;

                 inq[v] = ;

                 Q.push(v);

             }

         }

     }

 }

 int main()

 {

     while (scanf("%d%d",&n,&m)==)

     {

         for (int i = ; i < maxn; i++) {

             E[i].clear(); inq[i] = , d[i] = 1e9;

         }

         for (int i = ; i < m; i++) {

             int x, y, z;

             scanf("%d%d%d", &x, &y, &z);

             E[x].push_back(make_pair(y, z));

             E[y].push_back(make_pair(x, z));

         }

         scanf("%d%d", &s, &t);

         SPFA(s);

         if (d[t] == 1e9)

             printf("-1\n");

         else

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

     }

     return ;

 }