#include <bits/stdc++.h>
using namespace std;
const int MAXN = 3e5 + 10;
const int INF = 2e9 + 7;
int n, m, s, t, g[MAXN];
pair<int, int> vec[MAXN];
int get(int f) {
  int ret = 0;
  for (int i = 0; ret < INF && i + 1 < m; i++) {
    int dis = g[i + 1] - g[i];
    if (dis > f) return INF;
    ret += dis << 1;
    int z = min(dis, f - dis);
    ret -= z;
  }
  return ret;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> m >> s >> t;
  for (int i = 0; i < n; i++) cin >> vec[i].first >> vec[i].second;
  for (int i = 0; i < m; i++) cin >> g[i];
  g[m++] = 0;
  g[m++] = s;
  sort(g, g + m);
  int b = 1, e = 1e9, ret = 2e9;
  while (b <= e) {
    int mid = b + e >> 1, mx = 0;
    for (int i = 0; i < n; i++)
      if (vec[i].first <= mid) mx = max(mx, vec[i].second);
    if (get(mx) <= t)
      ret = mid, e = mid - 1;
    else
      b = mid + 1;
  }
  if (ret > 1e9 + 7) ret = -1;
  cout << ret << "\n";
  return 0;
}
