#include <bits/stdc++.h>
using namespace std;
long long start, endi, cars, stations, street, time_, station, max_distance,
    ans;
pair<long long, long long> cn;
vector<pair<long long, long long> > myvec;
vector<long long> spaces, store;
bool can(long long fuel) {
  long long check = 0;
  for (long long i = 0; i < spaces.size(); i++) {
    check += min(fuel - spaces[i], spaces[i]);
    if (fuel < 0) return 0;
    check += (spaces[i] - (min(fuel - spaces[i], spaces[i]))) * 2;
  }
  if (check <= time_) {
    return 1;
  } else
    return 0;
}
void binary(long long mid) {
  if (start > endi) return;
  if (can(mid)) {
    endi = mid - 1;
    ans = mid;
  } else {
    start = mid + 1;
  }
  binary((start + endi) / 2);
}
int main() {
  scanf("%lld %lld %lld %lld", &cars, &stations, &street, &time_);
  for (long long i = 0; i < cars; i++) {
    scanf("%lld %lld", &cn.first, &cn.second);
    myvec.push_back(cn);
  }
  sort(myvec.begin(), myvec.end());
  for (long long i = cars - 2; i >= 0; i--) {
    myvec[i].first = min(myvec[i + 1].first, myvec[i].first);
  }
  store.push_back(0);
  store.push_back(street);
  for (long long i = 0; i < stations; i++) {
    scanf("%lld", &station);
    store.push_back(station);
  }
  sort(store.begin(), store.end());
  for (long long i = 1; i < store.size(); i++) {
    long long distance = store[i] - store[i - 1];
    spaces.push_back(distance);
    max_distance = max(max_distance, distance);
  }
  start = max_distance;
  endi = street;
  binary((start + endi) / 2);
  if (ans == 0) {
    printf("-1\n");
    return 0;
  } else {
    for (int i = 0; i < myvec.size(); i++) {
      if (ans <= myvec[i].second) {
        printf("%lld", myvec[i].first);
        return 0;
      }
    }
  }
  printf("-1\n");
}
