#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> PII;
const int INF = 0x3f3f3f3f;
const int M = 2e5 + 5, N = 1005;
// 存图
int idx, h[N], e[M], w[M], ne[M];
void add(int a, int b, int c) {
    e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx++;
}
int n, m;   // n个点，m条边
int S;      // 出发点
int dis[N]; // 距离数组
bool st[N]; // Dijkstra是不是入过队列

void dijkstra() {
    priority_queue<PII, vector<PII>, greater<PII>> q;
    q.push({0, S});
    dis[S] = 0;
    while (q.size()) {
        auto t = q.top();
        int u = t.second;
        q.pop();
        if (st[u]) continue;
        st[u] = true;

        for (int i = h[u]; ~i; i = ne[i]) {
            int j = e[i];
            if (dis[j] > dis[u] + w[i]) {
                dis[j] = dis[u] + w[i];
                q.push({dis[j], j});
            }
        }
    }
}
int main() {
    while (cin >> n >> m >> S) {
        // 初始化
        memset(st, 0, sizeof st);
        memset(h, -1, sizeof h);
        memset(dis, 0x3f, sizeof dis);
        idx = 0;
        int ans = INF;

        while (m--) {
            int a, b, c;
            cin >> a >> b >> c;
            add(b, a, c); // 反向建边
        }
        // 最短路
        dijkstra();
        int T; // T个终点
        int x; // 终点ID
        cin >> T;
        while (T--) {
            cin >> x;
            ans = min(ans, dis[x]);
        }
        printf("%d\n", ans == INF ? -1 : ans);
    }
    return 0;
}