#include <bits/stdc++.h>
using namespace std;
int n, m, x, y, z, k, w, need, ans, tmp, s, t;
int A[200005], B[200005], G[200005];
int high, low, mid;
int main() {
  scanf("%d %d %d %d", &n, &k, &s, &t);
  for (int i = (0); i < (n); i++) scanf("%d %d", &A[i], &B[i]);
  for (int i = (0); i < (k); i++) scanf("%d", &G[i]);
  sort(G, G + k);
  high = 1000000001;
  low = 0;
  need = s * 2 - t;
  if (need <= 0) need = 0;
  G[k] = s;
  while (high - low > 1) {
    mid = (high + low) / 2;
    x = 0;
    y = 1;
    tmp = 0;
    for (int i = (0); i < (k + 1); i++) {
      if ((G[i] - x) * 2 <= mid)
        tmp += (G[i] - x);
      else if ((G[i] - x) > mid) {
        y = 0;
        break;
      } else
        tmp += (mid - (G[i] - x));
      x = G[i];
    }
    if (y == 0)
      low = mid;
    else if (tmp >= need)
      high = mid;
    else
      low = mid;
  }
  ans = 1234567890;
  for (int i = (0); i < (n); i++)
    if (B[i] >= high) ans = min(ans, A[i]);
  if (ans == 1234567890) ans = -1;
  printf("%d\n", ans);
  return 0;
}
