#include <bits/stdc++.h>
using namespace std;
void die() {
  cout << -1 << endl;
  exit(0);
}
const int maxN = 100 * 1000 * 3 + 100;
pair<int, int> a[maxN];
int p[maxN];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, k, s, t;
  cin >> n >> k >> s >> t;
  if (t < s) die();
  for (int i = 0; i < n; i++) cin >> a[i].second >> a[i].first;
  k++;
  for (int i = 1; i < k; i++) cin >> p[i];
  p[k++] = s;
  sort(p, p + k);
  sort(a, a + n);
  int st = -1, en = n;
  while (en - st > 1) {
    int m = (st + en) / 2;
    int cap = a[m].first;
    int speed = max(2 * s - t, 0);
    bool canDo = true;
    for (int i = 1; i < k; i++)
      if (p[i] - p[i - 1] > cap) {
        canDo = false;
        break;
      } else
        speed -= min(speed, min(p[i] - p[i - 1], cap - (p[i] - p[i - 1])));
    if (canDo && speed == 0)
      en = m;
    else
      st = m;
  }
  if (en == n) die();
  int mn = a[en].second;
  for (int i = en + 1; i < n; i++) mn = min(mn, a[i].second);
  cout << mn << endl;
}
