#include <bits/stdc++.h>
using namespace std;
const int inf = 2100000000;
int s, t, ans, i, j, k, n, m, a[310001], mid, b[310001], g[310001], l, r;
bool check(int x) {
  int i, j, k = 0;
  for (i = 1; i <= m + 1; i++) {
    if (g[i] - g[i - 1] > x) return 0;
    k += min(x - g[i] + g[i - 1], g[i] - g[i - 1]);
  }
  return k >= 2LL * (long long)s - t;
}
int main() {
  scanf("%d%d%d%d", &n, &m, &s, &t);
  for (k = 0, i = 1; i <= n; i++) scanf("%d%d", &a[i], &b[i]), k = max(k, b[i]);
  for (i = 1; i <= m; i++) scanf("%d", &g[i]);
  sort(g + 1, g + 1 + m);
  g[0] = 0;
  g[m + 1] = s;
  if (!check(k)) {
    puts("-1");
    return 0;
  }
  for (l = 0, r = k; l < r - 1;) {
    mid = ((long long)l + (long long)r) / 2LL;
    if (check(mid))
      r = mid;
    else
      l = mid + 1;
  }
  k = (check(l)) ? l : r;
  for (i = 1, ans = inf; i <= n; i++)
    if (b[i] >= k) ans = min(ans, a[i]);
  printf("%d\n", ans);
  return 0;
}
