#include<iostream>

 #include<cstdio>

 #include<cstring>

 #include<queue>

 #include<algorithm>

 using namespace std;

 const int N = , M=;

 const int INF = 0x3f3f3f3f;

 struct node

 {

     int to, w, next;

 };

 node edge[M];

 int head[N], dist[N], outq[N];

 bool vis[N];

 int tot;

 bool SPFA(int s, int n )

 {

     int i,k;

     for(i=;i<=n;i++) dist[i]=INF;

     memset(vis,,sizeof(vis));

     memset(outq,,sizeof(outq));

     queue<int > q;

     while(!q.empty()) q.pop();

     vis[s]=;

     dist[s]=;

     q.push(s);

     while(!q.empty())

     {

         int u=q.front();

         q.pop();

         vis[u]=;

         outq[u]++;

         if(outq[u]>n) return  ;

         k=head[u];

         while(k>=)

         {

             if(dist[edge[k].to]-edge[k].w>dist[u])

             {

                 dist[edge[k].to]=dist[u]+edge[k].w;

                 if(!vis[edge[k].to])

                 {

                     vis[edge[k].to]=;

                     q.push(edge[k].to);

                 }

             }

             k=edge[k].next;

         }

     }

     return ;

 }

 void addedge(int i,int j,int w)

 {

     edge[tot].to=j;

     edge[tot].w=w;

     edge[tot].next=head[i];

     head[i]=tot++;

 }

 void init()

 {

     tot=;

     memset(head,-,sizeof(head));

 }

 int main()

 {

     //freopen("test.txt","r",stdin);

     int i,j,k,n,m,t,s;

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

     {

         init();

         while(m--)

         {

             scanf("%d%d%d",&i,&j,&k);

             addedge(i,j,k);

         }

         scanf("%d",&k);

         for(i=;i<k;i++)

         {

             scanf("%d",&s);

             addedge(n+,s,);

         }

         SPFA(n+,n+);

         if(dist[t]==INF) printf("-1\n");

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

     }

     return ;

 }