#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <map>
#include <vector>
using namespace std;
const int N = 1005;
const int inf = 0X7000000;
int n,m,s,p,q,t,w;
int d[N][N],fa[N],dist[N],ans;
int ww[N];
void init(){
    for(int i = 0; i <= n; i++){
        for(int j = 0; j <= n; j++)
            d[i][j] = inf;
        fa[i] = i; dist[i] = inf;
    }
}
int find(int x){
    if(x == fa[x]) return x;
    return fa[x] = find(fa[x]);
}
void Union(int x, int y){
    x = find(x);
    y = find(y);
    if(x!=y) fa[y] = x;
}
void dij(int start){
    for(int i = 0; i <= n; i++){
        dist[i] = d[start][i];
    }
    dist[start] = 0;
    for(int i = 1; i <= n; i++){
        int mn = inf;
        int pos = start;
        for(int j = 1; j <=n; j++){
            if(fa[j] != start && dist[j] < mn){
                pos = j;
                mn = dist[j];
            }
        }
        Union(start,pos);
        for(int j = 1; j <= n; j++){
            if(fa[j] != start && (dist[pos]+d[pos][j]) < dist[j])
                dist[j] = dist[pos]+d[pos][j];
        }
    }
    ans = dist[s];
}
int main(){
    while(~scanf("%d %d %d",&n, &m,&s)){
        ans = inf;
        init();
        while(m--){
            scanf("%d %d %d",&p, &q, &t);
            if(t < d[p][q]) d[p][q] = t; //好像巴士不是双向的。。
        }
        scanf("%d",&w);
        for(int i = 0; i < w; i++){
            scanf("%d", &m);
            d[0][m] = 0;
        }
        dij(0);
        if(ans == inf) ans = -1;
        printf("%d\n", ans);
    }
    return 0;
}