#include <bits/stdc++.h>
using namespace std;
const int maxn = 10005;
const int maxm = 1000005;
const int INF = 0x3f3f3f3f;
int head[maxn], cur[maxn], nx[maxm << 1], to[maxm << 1], flow[maxm << 1],
    ppp = 0;
struct Dinic {
  int dis[maxn];
  int s, t;
  int ans;
  void init() {
    memset(head, -1, sizeof(head));
    ppp = 0;
  }
  void AddEdge(int u, int v, int c) {
    to[ppp] = v;
    flow[ppp] = c;
    nx[ppp] = head[u];
    head[u] = ppp++;
    swap(u, v);
    to[ppp] = v;
    flow[ppp] = 0;
    nx[ppp] = head[u];
    head[u] = ppp++;
  }
  bool BFS() {
    memset(dis, -1, sizeof(dis));
    dis[t] = 1;
    queue<int> Q;
    Q.push(t);
    while (!Q.empty()) {
      int x = Q.front();
      Q.pop();
      for (int i = head[x]; ~i; i = nx[i]) {
        if (flow[i ^ 1] && dis[to[i]] == -1) {
          dis[to[i]] = dis[x] + 1;
          Q.push(to[i]);
        }
      }
    }
    return dis[s] != -1;
  }
  int DFS(int x, int maxflow) {
    if (x == t || !maxflow) {
      ans += maxflow;
      return maxflow;
    }
    int ret = 0, f;
    for (int &i = cur[x]; ~i; i = nx[i]) {
      if (dis[to[i]] == dis[x] - 1 && (f = DFS(to[i], min(maxflow, flow[i])))) {
        ret += f;
        flow[i] -= f;
        flow[i ^ 1] += f;
        maxflow -= f;
        if (!maxflow) break;
      }
    }
    return ret;
  }
  int solve(int source, int tank) {
    s = source;
    t = tank;
    ans = 0;
    while (BFS()) {
      memcpy(cur, head, sizeof(cur));
      DFS(s, INF);
    }
    return ans;
  }
} dinic;
vector<pair<int, int> > edge[605];
int cnt[605], dis[605][605];
int n, m, e;
void floyd() {
  for (int k = 1; k <= m; k++) {
    for (int i = 1; i <= m; i++) {
      for (int j = 1; j <= m; j++) {
        dis[i][j] = min(dis[i][k] + dis[k][j], dis[i][j]);
      }
    }
  }
}
int main() {
  int k;
  ios::sync_with_stdio(0);
  cin >> m >> e >> n >> k;
  for (int i = 1, tmp; i <= n; i++) {
    cin >> tmp;
    cnt[tmp]++;
  }
  for (int i = 1; i <= m; i++) {
    for (int j = 1; j <= m; j++) {
      dis[i][j] = INF;
    }
  }
  for (int i = 0, u, v, val; i < e; i++) {
    cin >> u >> v >> val;
    if (u == v) continue;
    if (dis[u][v] > val) dis[u][v] = dis[v][u] = val;
  }
  floyd();
  int front = 0, back = 1731311;
  while (front <= back) {
    int mid = (front + back) / 2;
    dinic.init();
    int s = 0, e = 2 * m + 1;
    for (int i = 1; i <= m; i++) {
      dinic.AddEdge(s, i, cnt[i]);
      dinic.AddEdge(m + i, e, 1);
    }
    for (int i = 1; i <= m; i++) {
      for (int j = 1; j <= m; j++) {
        if (dis[i][j] <= mid || i == j) dinic.AddEdge(i, m + j, INF);
      }
    }
    int Max_Flow = dinic.solve(s, e);
    if (Max_Flow >= k) {
      back = mid - 1;
    } else {
      front = mid + 1;
    }
  }
  if (front <= 1731311)
    cout << front << endl;
  else
    cout << -1 << endl;
  return 0;
}
