#include <bits/stdc++.h>
using namespace std;
int n, m, p, r, dis[610][610], occ[610];
namespace MaxFlow {
const int N = 10000, M = 2000000;
int head[N], cur[N], dep[N], cnt, S, T, res;
struct node {
  int to, next, val;
} edge[M];
void ae(int u, int v, int w) {
  edge[cnt].next = head[u], edge[cnt].to = v, edge[cnt].val = w,
  head[u] = cnt++;
  edge[cnt].next = head[v], edge[cnt].to = u, edge[cnt].val = 0,
  head[v] = cnt++;
}
queue<int> q;
inline bool bfs() {
  memset(dep, 0, sizeof(dep)), q.push(S), dep[S] = 1;
  while (!q.empty()) {
    register int x = q.front();
    q.pop();
    for (register int i = cur[x] = head[x]; i != -1; i = edge[i].next)
      if (edge[i].val && !dep[edge[i].to])
        dep[edge[i].to] = dep[x] + 1, q.push(edge[i].to);
  }
  return dep[T] > 0;
}
bool reach;
inline int dfs(int x, int flow) {
  if (x == T) {
    res += flow;
    reach = true;
    return flow;
  }
  int used = 0;
  for (register int &i = cur[x]; i != -1; i = edge[i].next) {
    if (!edge[i].val || dep[edge[i].to] != dep[x] + 1) continue;
    register int ff = dfs(edge[i].to, min(edge[i].val, flow - used));
    if (ff) {
      edge[i].val -= ff;
      edge[i ^ 1].val += ff;
      used += ff;
      if (used == flow) break;
    }
  }
  return used;
}
inline void Dinic() {
  while (bfs()) {
    reach = true;
    while (reach) reach = false, dfs(S, 0x3f3f3f3f);
  }
}
}  // namespace MaxFlow
using namespace MaxFlow;
int che(int ip) {
  memset(head, -1, sizeof(head)), cnt = res = 0;
  for (int i = 1; i <= n; i++) ae(S, i, occ[i]), ae(i + n, T, 1);
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= n; j++)
      if (dis[i][j] <= ip) ae(i, j + n, 0x3f3f3f3f);
  Dinic();
  return res >= r;
}
int main() {
  scanf("%d%d%d%d", &n, &m, &p, &r), memset(dis, 0x3f3f3f3f, sizeof(dis)),
      S = n * 2 + 1, T = n * 2 + 2;
  for (int i = 1; i <= n; i++) dis[i][i] = 0;
  for (int i = 1, x; i <= p; i++) scanf("%d", &x), occ[x]++;
  for (int i = 1, x, y, z; i <= m; i++)
    scanf("%d%d%d", &x, &y, &z), dis[x][y] = dis[y][x] = min(dis[x][y], z);
  for (int k = 1; k <= n; k++)
    for (int i = 1; i <= n; i++)
      for (int j = 1; j <= n; j++)
        dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
  int L = 0, R = 1731311;
  while (L < R) {
    int mid = (L + R) >> 1;
    if (che(mid))
      R = mid;
    else
      L = mid + 1;
  }
  if (!che(R))
    puts("-1");
  else
    printf("%d\n", R);
  return 0;
}
