#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
int main() {
  int n, k, s, t;
  scanf("%d %d %d %d", &n, &k, &s, &t);
  if (t < s) {
    cout << -1;
    return 0;
  }
  std::vector<std::pair<int, int> > var(n);
  for (int i = 0; i < n; i++) {
    scanf("%d %d", &var[i].first, &var[i].second);
  }
  std::vector<int> g(k);
  for (int i = 0; i < k; i++) {
    scanf("%d", &g[i]);
  }
  g.push_back(0);
  g.push_back(s);
  sort((g).begin(), (g).end());
  std::vector<int> d;
  for (int i = 0; i < k + 1; i++) {
    d.push_back(g[i + 1] - g[i]);
  }
  sort((d).begin(), (d).end());
  long long l = 0;
  long long r = 2000000000;
  while (r - l > 1) {
    long long m = (r + l) / 2;
    long long cur = 0;
    for (long long x : d) {
      if (x > m)
        cur = t + 1;
      else {
        cur += 2 * x - min(m - x, x);
      }
    }
    if (cur <= t)
      r = m;
    else
      l = m;
  }
  int ans = 1000000001;
  for (auto x : var) {
    if (x.second >= r) ans = min(x.first, ans);
  }
  if (ans == 1000000001) ans = -1;
  cout << ans;
}
