/*

 ∧＿∧
( ･ω･｡)つ━☆・*。
⊂　 ノ 　　　・゜
しーＪ　　 Accepted

*/



// #pragma GCC optimize("O3")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define ll long long
#define all(x) begin(x), end(x)
#define x first
#define y second
#define int long long

using namespace std;
using namespace __gnu_pbds;

typedef long double ld;
template<typename T>
using kawaii_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

const ld PI = atan2(0, -1);

void seriy() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cout << fixed << setprecision(14);
    #ifdef _offline
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
}

const int MAXN = 1e6 + 10;
const int MAXM = 600;
const int INF = 1e18;
const int BASE = 47;
const int MOD = 1e9 + 7;
const int MAXLOG = 21;

vector<vector<pair<int, int>>> g;
vector<vector<int>> g2;
vector<int> gas, isgas;

void dijkstra(int a, vector<int> &d) {
    fill(all(d), INF);
    d[a] = 0;
    set<pair<int, int>> st;
    st.insert({0, a});
    while(st.size()) {
        int u = st.begin()->y;
        st.erase(st.begin());
        for(auto v : g[u]) {
            if(d[u] + v.y < d[v.x]) {
                st.erase({d[v.x], v.x});
                d[v.x] = d[u] + v.y;
                st.insert({d[v.x], v.x});
            }
        }
    }
}

signed main() {
    seriy();
    int k, n, m, st, en;
    cin >> k >> n >> m >> st >> en;
    st--;
    en--;
    g.resize(n);
    g2.resize(n);
    isgas.resize(n);
    for(int i = 0; i < m; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        u--;
        v--;
        g[u].push_back({v, w});
        g[v].push_back({u, w});
    }
    int l;
    cin >> l;
    gas.resize(l);
    for(int i = 0; i < l; i++) {
        cin >> gas[i];
        gas[i]--;
        isgas[gas[i]] = 1;
    }
    isgas[st] = 1;
    isgas[en] = 1;
    gas.push_back(st);
    gas.push_back(en);
    vector<vector<int>> kek(n, vector<int>(n, INF));
    for(int i = 0; i < n; i++) {
        if(isgas[i]) {
            dijkstra(i, kek[i]);
        }
    }
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < n; j++) {
            if(i == j) {
                continue;
            }
            // cerr << kek[i][j] << " ";
            if(kek[i][j] <= k && isgas[j] && isgas[i]) {
                cerr << i << " " << j << '\n';
                g2[i].push_back(j);
            }
        }
        cerr << '\n';
    }
    queue<pair<int, int>> q;
    q.push({st, 0});
    vector<bool> used(n);
    used[st] = 1;
    while(q.size()) {
        pair<int, int> u = q.front();
        q.pop();
        if(u.x == en) {
            cerr << u.y - 1 << '\n';
            return cout << u.y - 1, 0;
        }
        for(auto v : g2[u.x]) {
            if(!used[v]) {
                used[v] = 1;
                q.push({v, u.y + 1});
            }
        }
    }
    cout << -1;
    return 0;
}