/*

 ∧＿∧
( ･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 = 10000 + 10;
const int MAXL = 510;
const int INF = 1e9 + 7;
const int BASE = 47;
const int MOD = 1e9 + 7;
const int MAXLOG = 51;
const ld EPS = 1e-6;

struct pt {
    int u, left, cnt;
};

int k, n, m, s, f;
vector<vector<pair<int, int>>> g, g2;
vector<bool> used(MAXN);

signed main() {
    seriy();
    cin >> k >> n >> m >> s >> f;
    s--;
    f--;
    g.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});
    }
    vector<bool> is(n);
    int l;
    cin >> l;
    int p[l];
    for(int i = 0; i < l; i++) {
        cin >> p[i];
        p[i]--;
        is[p[i]] = 1;
    }
    deque<pt> q;
    q.push_back({s, k, 0});
    vector<int> was(n, INF);
    int res = INF;
    while(q.size()) {
        pt u = q.front();
        q.pop_front();
        was[u.u] = min(was[u.u], u.cnt);
        if(u.u == f) {
            res = min(res, u.cnt);
        }
        for(auto v : g[u.u]) {
            if(u.left >= v.y && was[v.x] >= was[u.u]) {
                q.push_front({v.x, u.left - v.y, u.cnt});
                if(is[v.x]) {
                    q.push_back({v.x, k, u.cnt + 1});
                }
            }
        }
    }
    cout << ((res == INF) ? -1 : res);
    return 0;
}