#include <bits/stdc++.h>
using namespace std;
const int p = 31, N = 1e5 + 10, M = (long long int)1e9 + 1;
const int mod = 1e9 + 7;
bool is(vector<long long int> g, long long int t, long long int v) {
  long long int i, j, dist, f, ti = 0;
  long long int x1, x2, k = g.size();
  for (i = 1; i < k; i++) {
    dist = g[i] - g[i - 1];
    f = v;
    x1 = f - dist;
    if (x1 < 0) return false;
    x1 = min(dist, f - dist);
    x2 = dist - x1;
    ti += x1 + 2 * x2;
    if (ti > t) return false;
  }
  return true;
}
int main() {
  ios_base::sync_with_stdio(0);
  long long int n, k, s, t;
  cin >> n >> k >> s >> t;
  long long int i;
  vector<pair<long long int, long long int> > a(n);
  for (i = 0; i < n; i++) {
    long long int c, v;
    cin >> c >> v;
    a[i] = {v, c};
  }
  vector<long long int> g(k + 2);
  g[0] = 0;
  for (i = 1; i <= k; i++) cin >> g[i];
  g[k + 1] = s;
  sort(g.begin(), g.end());
  long long int lo = 1, hi = 1e9 + 10, ok = 0;
  while (lo < hi) {
    long long int m = lo + (hi - lo) / 2;
    if (is(g, t, m)) {
      ok = 1;
      hi = m;
    } else
      lo = m + 1;
  }
  long long int ans = INT_MAX, capa = lo;
  for (i = 0; i < n; i++) {
    if (a[i].first >= capa) ans = min(ans, a[i].second);
  }
  if (ans == INT_MAX)
    cout << -1;
  else
    cout << ans;
  return 0;
}
