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#include<stdio.h>

#include<math.h>

#include<string.h>

#include<vector>

#include<algorithm>

using namespace std;

const int maxn = 1111;

vector<int>abc[maxn];

int ji[maxn], tt[maxn][maxn], yy[maxn];

struct aaa{

    int node, time;

}dt[maxn*maxn];

bool cmp(const aaa&a, const aaa&b){ return a.time < b.time; }

int main()

{

    int n, m, mubiao;

    while (~scanf("%d%d%d", &n, &m, &mubiao))

    {

        int i, j;

        for (i = 0; i < maxn; i++) for (j = 0; j < maxn; j++) tt[i][j] = 999999999;

        for (i = 0; i < maxn; i++) ji[i] = 999999999, abc[i].clear();

        for (i = 0; i < m; i++)

        {

            int u, v, t;

            scanf("%d%d%d", &u, &v, &t);

            if (t < tt[v][u])

            {

                tt[v][u] = t;

                abc[v].push_back(u);

            }

        }

        int dd; scanf("%d", &dd);

        for (i = 0; i < dd; i++) scanf("%d", &yy[i]);

        int b = 0;

        dt[0].node = mubiao;

        dt[0].time = 0;

        for (i = 0; i <= b; i++)

        {

            for (j = 0; j < abc[dt[i].node].size(); j++)

            {

                if (dt[i].time + tt[dt[i].node][abc[dt[i].node][j]] < ji[abc[dt[i].node][j]])

                {

                    b++;

                    dt[b].node = abc[dt[i].node][j];

                    dt[b].time = dt[i].time + tt[dt[i].node][abc[dt[i].node][j]];

                    ji[abc[dt[i].node][j]] = dt[i].time + tt[dt[i].node][abc[dt[i].node][j]];

                }

            }

        }

        int ans = 999999999;

        for (i = 0; i < dd; i++) if (ji[yy[i]] < ans) ans = ji[yy[i]];

        if (ans == 999999999) printf("-1\n");

        else printf("%d\n", ans);

    }

    return 0;

}