#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, k, s, t;
  long long cost[200001], fuel[200001];
  long long stn[200001];
  ios::sync_with_stdio(false);
  cin >> n >> k >> s >> t;
  long long cnt = max(2 * s - t, 0LL);
  long long high = 1000000001;
  long long low = 0;
  for (int i = 0; i < n; i++) {
    cin >> cost[i] >> fuel[i];
    high = max(high, fuel[i] + 1);
    low = min(low, fuel[i] - 1);
  }
  stn[0] = 0;
  stn[1] = s;
  for (int i = 2; i < k + 2; i++) {
    cin >> stn[i];
  }
  if (t < s) {
    cout << -1 << endl;
    return 0;
  }
  sort(stn, stn + k + 2);
  long long mid;
  while (high - low > 1) {
    mid = (high + low) / 2;
    bool bse = 0;
    long long count = 0;
    for (int i = 0; i < k + 1; i++) {
      if (stn[i + 1] - stn[i] > mid) {
        bse = 1;
        break;
      }
      count += min(mid - (stn[i + 1] - stn[i]), stn[i + 1] - stn[i]);
    }
    if (count < cnt) {
      bse = 1;
    }
    if (bse) {
      low = mid;
    } else {
      high = mid;
    }
  }
  long long ans = 2000000001;
  for (int i = 0; i < n; i++) {
    if (fuel[i] >= high) {
      ans = min(ans, cost[i]);
    }
  }
  if (ans != 2000000001)
    cout << ans << endl;
  else
    cout << -1 << endl;
}
