#include <bits/stdc++.h>
using namespace std;
template <class T>
bool uin(T &a, T b) {
  return a > b ? (a = b, true) : false;
}
template <class T>
bool uax(T &a, T b) {
  return a < b ? (a = b, true) : false;
}
const int maxn = 601;
int d[maxn][maxn];
int st[maxn], vis[maxn], match[maxn];
vector<int> w[maxn];
bool dfs(int v) {
  if (vis[v]) return false;
  vis[v] = 1;
  for (int u : w[v]) {
    if (match[u] == -1 || dfs(match[u])) {
      match[u] = v;
      return true;
    }
  }
  return false;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.precision(10);
  cout << fixed;
  int v, e, n, k;
  cin >> v >> e >> n >> k;
  for (int i = 0; i < (int)(v); ++i)
    for (int j = 0; j < (int)(v); ++j) d[i][j] = 1e9;
  for (int i = 0; i < (int)(v); ++i) d[i][i] = 0;
  for (int i = 0; i < (int)(n); ++i) cin >> st[i], --st[i];
  for (int i = 0; i < (int)(e); ++i) {
    int x, y, t;
    cin >> x >> y >> t;
    --x;
    --y;
    uin(d[x][y], t);
    uin(d[y][x], t);
  }
  for (int k = 0; k < (int)(v); ++k)
    for (int i = 0; i < (int)(v); ++i)
      for (int j = 0; j < (int)(v); ++j) uin(d[i][j], d[i][k] + d[k][j]);
  int L = -1, R = 1e9;
  while (R - L > 1) {
    int M = (L + R) / 2;
    for (int i = 0; i < (int)(n); ++i) w[i].clear();
    for (int i = 0; i < (int)(n); ++i)
      for (int j = 0; j < (int)(v); ++j)
        if (d[st[i]][j] <= M) w[i].push_back(j);
    for (int j = 0; j < (int)(v); ++j) match[j] = -1;
    int res = 0;
    for (int i = 0; i < (int)(n); ++i) {
      for (int j = 0; j < (int)(n); ++j) vis[j] = 0;
      res += int(dfs(i));
    }
    (res >= k ? R : L) = M;
  }
  if (R > 1e8) R = -1;
  cout << R << '\n';
  return 0;
}
