#include<stdio.h>
#include<string.h>
#define N 1500
#define INF 0x3f3f3f
int n,t,f;
int map[N][N];
int s[N];
int book[N];
int d[N];
void Dijkstra(int x)
{
    int i,j;
    memset(book,0,sizeof(book));
    book[x]=1;//終端
    for(i=1; i<=n; i++)
    {
        d[i]=map[x][i];
    }
    d[x]=0;
    //初始化;
    for(i=1; i<=n; i++)
    {
        int index=-1;
        int max=INF;
        for(j=1; j<=n; j++)
        {
            if(book[j]==0&&d[j]<max)
            {
                max=d[j];
                index=j;
            }
        }
        if(index==-1)
            break;
        book[index]=1;
        for(j=1; j<=n; j++)
        {
            if(book[j]==0&&d[j]>map[index][j]+max)
            {
                d[j]=map[index][j]+max;
            }
        }
    }
    int max=INF;

    for(int k=1; k<=f; k++)
    {
        if(max>d[s[k]])
            max=d[s[k]];
    }
    //printf("%d ",d[i]);

    //printf("\n");
    if(max>=INF)
        printf("-1\n");
    else
        printf("%d\n",max);
}
int main()
{
    int i,j,k,m,u,v,w;

    while(scanf("%d%d%d",&n,&m,&t)!=EOF)
    {
        memset(map,INF,sizeof(map));
        for(i=0; i<m; i++)
        {
            scanf("%d%d%d",&u,&v,&w);
            if(w<map[v][u])
            {
                map[v][u]=w;//倒著處理;
            }
        }

        scanf("%d",&f);
        for(i=1; i<=f; i++)
        {
            scanf("%d",&s[i]);

        }

        Dijkstra(t);

    }

    return 0;
}