#include <bits/stdc++.h>
using namespace std;
const long long inf = 4e18;
const long long N = 2e5 + 10;
void testCase() {
  long long n, k, s, t;
  cin >> n >> k >> s >> t;
  vector<long long> cost(n), cap(n), f(k);
  for (long long i = 0; i < n; i++) cin >> cost[i] >> cap[i];
  for (long long &i : f) cin >> i;
  f.push_back(0);
  f.push_back(s);
  sort(begin(f), end(f));
  auto isPos = [&](long long lim) {
    long long totslow = t - s;
    for (long long i = 1; i <= k + 1; i++) {
      long long diff = f[i] - f[i - 1];
      long long fast = lim - diff;
      if (fast < 0) return false;
      long long slow = max(0ll, diff - fast);
      totslow -= slow;
      if (totslow < 0) return false;
    }
    return true;
  };
  long long mi = 0, ma = inf;
  while (mi + 1 < ma) {
    long long mid = (mi + ma) / 2;
    if (isPos(mid))
      ma = mid;
    else
      mi = mid;
  }
  long long ans = inf;
  for (long long i = 0; i < n; i++) {
    if (cap[i] >= ma) ans = min(ans, cost[i]);
  }
  cout << (ans == inf ? -1 : ans) << '\n';
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr), cout.tie(nullptr);
  long long t_c = 1;
  while (t_c--) testCase();
}
