#include <bits/stdc++.h>
using namespace std;
bool check(int x, int t, int n, vector<int>& g) {
  int u = 0;
  for (int i = 0; i <= n; i++) {
    int d = g[i + 1] - g[i];
    if (x < d) return false;
    u += d * 2 - min(d, x - d);
    if (t < u) return false;
  }
  return true;
}
int main() {
  int n, m, s, t, ans = -1;
  scanf("%d%d%d%d", &n, &m, &s, &t);
  vector<pair<int, int> > second(n);
  vector<int> g(m);
  for (int i = 0; i < n; i++)
    scanf("%d%d", &second[i].first, &second[i].second);
  for (int i = 0; i < m; i++) scanf("%d", &g[i]);
  g.push_back(0);
  g.push_back(s);
  sort(g.begin(), g.end());
  sort(second.begin(), second.end());
  for (int i = 1; i < n; i++)
    second[i].second = max(second[i].second, second[i - 1].second);
  for (int l = 0, r = n; l < r;) {
    int k = (l + r) >> 1;
    if (!check(second[k].second, t, m, g))
      l = k + 1;
    else {
      ans = second[k].first;
      r = k;
    }
  }
  printf("%d\n", ans);
}
