#include <bits/stdc++.h>
using namespace std;
const int INF = 0x6fffffff;
const int MINF = 0x80000000;
const long long mod = 1000000007;
const int cons = 100001;
const double pi = 3.141592653589793;
vector<int> pos;
bool isOk(int x, int t) {
  double res = 0;
  for (int i = 1; i < pos.size(); i++) {
    int diff = pos[i] - pos[i - 1];
    int l = -1;
    int r = x + 1;
    while (l + 1 < r) {
      int mid = l + r >> 1;
      int y = x - mid;
      double avail = (double)y / 2 + mid;
      if (avail >= (double)diff)
        r = mid;
      else
        l = mid;
    }
    if (r == x + 1) return false;
    diff -= r;
    res += (double)r * 2;
    res += min((double)diff, ((double)x - r) / 2);
  }
  return res <= (double)t;
}
int main() {
  int n, k, s, t;
  cin >> n >> k >> s >> t;
  map<int, int> M;
  for (int i = 0; i < n; i++) {
    int c, v;
    scanf("%d%d", &c, &v);
    M[c] = max(M[c], v);
  }
  int cur = 0;
  vector<pair<int, int> > dat;
  for (auto it : M) {
    if (cur < it.second) {
      cur = it.second;
      dat.push_back(it);
    }
  }
  pos.resize(k);
  for (int i = 0; i < k; i++) {
    scanf("%d", &pos[i]);
  }
  pos.push_back(0);
  pos.push_back(s);
  sort(pos.begin(), pos.end());
  int L = -1;
  int R = dat.size();
  while (L + 1 < R) {
    int mid = L + R >> 1;
    if (isOk(dat[mid].second, t))
      R = mid;
    else
      L = mid;
  }
  if (R == dat.size())
    puts("-1");
  else
    printf("%d\n", dat[R].first);
  return 0;
}
