#include <bits/stdc++.h>
using namespace std;
const int N = 805;
const int INF = 0x3f3f3f3f;
int n, m, k, lim;
struct Edge {
  int from, to, flow, cap;
  Edge(int f, int t, int fl, int c) : from(f), to(t), flow(fl), cap(c) {}
};
struct EK {
  int n;
  vector<Edge> E;
  vector<int> g[N];
  int p[N], df[N];
  bool vis[N];
  void init(int n) {
    this->n = n;
    for (int i = 1; i <= n; i++) g[i].clear();
    E.clear();
  }
  void addEdge(int u, int v, int c) {
    E.push_back(Edge(u, v, 0, c));
    E.push_back(Edge(v, u, 0, 0));
    int sz = E.size();
    g[u].push_back(sz - 2);
    g[v].push_back(sz - 1);
  }
  int bfs(int S, int T) {
    memset(df, 0, sizeof(df));
    memset(vis, 0, sizeof(vis));
    queue<int> Q;
    df[S] = 0x3f3f3f3f, vis[S] = 1;
    Q.push(S);
    while (!Q.empty()) {
      int u = Q.front();
      Q.pop();
      for (int i = 0; i < ((int)g[u].size()); i++) {
        Edge &e = E[g[u][i]];
        if (!vis[e.to] && e.cap > e.flow) {
          p[e.to] = g[u][i];
          vis[e.to] = 1;
          df[e.to] = min(df[e.from], e.cap - e.flow);
          Q.push(e.to);
        }
      }
      if (vis[T]) break;
    }
    for (int u = T; u != S; u = E[p[u]].from) {
      E[p[u]].flow += df[T];
      E[p[u] ^ 1].flow -= df[T];
    }
    return df[T];
  }
  int maxFlow(int S, int T) {
    int F = 0;
    while (1) {
      int D = bfs(S, T);
      if (!D) break;
      F += D;
    }
    return F;
  }
} T;
bool done[N];
vector<pair<int, int> > g[N];
int dis[N][N], st[N];
void dij(int s) {
  memset(dis[s], 0x3f, sizeof(dis[s]));
  memset(done, 0, sizeof(done));
  priority_queue<pair<int, int>, vector<pair<int, int> >,
                 greater<pair<int, int> > >
      Q;
  Q.push(make_pair(0, s));
  dis[s][s] = 0;
  while (!Q.empty()) {
    int u = Q.top().second;
    Q.pop();
    if (done[u]) continue;
    done[u] = 1;
    for (int i = 0; i < ((int)g[u].size()); i++) {
      int v = g[u][i].first, w = g[u][i].second;
      if (dis[s][v] > dis[s][u] + w) {
        dis[s][v] = dis[s][u] + w;
        Q.push(make_pair(dis[s][v], v));
      }
    }
  }
}
int tot;
bool check(int x) {
  T.init(n + tot + 2);
  int cur = 0;
  for (int i = 1; i <= n; i++) {
    if (st[i]) {
      T.addEdge(n + tot + 1, ++cur, st[i]);
      for (int j = 1; j <= n; j++)
        if (dis[i][j] <= x) {
          T.addEdge(cur, j + tot, 1);
        }
    }
    T.addEdge(i + tot, n + tot + 2, 1);
  }
  return T.maxFlow(n + tot + 1, n + tot + 2) >= lim;
}
int main() {
  scanf("%d%d%d%d", &n, &m, &k, &lim);
  for (int i = 0; i < k; i++) {
    int x;
    scanf("%d", &x);
    st[x]++;
  }
  for (int i = 1; i <= n; i++)
    if (st[i]) tot++;
  while (m--) {
    int u, v, w;
    scanf("%d%d%d", &u, &v, &w);
    g[u].push_back(make_pair(v, w));
    g[v].push_back(make_pair(u, w));
  }
  for (int i = 1; i <= n; i++) dij(i);
  int l = 0, r = 1731312;
  while (l + 1 < r) {
    int mid = (l + r) / 2;
    if (check(mid))
      r = mid;
    else
      l = mid;
  }
  int ans = check(l) ? l : r;
  printf("%d\n", ans > 1731311 ? -1 : ans);
  return 0;
}
