#include <bits/stdc++.h>
using namespace std;
const long long M = 1e14 + 10;
long long n, k, s, t, maxV = 0;
long long temp1, temp2;
map<long long, long long> cars;
vector<long long> stops;
vector<long long> dis;
bool check(long long v) {
  double time = 0;
  for (long long j = 0; j < dis.size(); j++) {
    if (1.0 * v / 2 >= dis[j]) {
      time += 1.0 * dis[j] / 2;
    } else {
      time += 1.0 * (3 * dis[j] - v) / 2;
    }
    if (time * 2 > t) {
      return false;
    }
  }
  return true;
}
long long search(long long start, long long end) {
  if (start > end) {
    return -1;
  }
  long long mid = (start + end) / 2;
  if (check(mid)) {
    long long next = search(start, mid - 1);
    if (next != -1) {
      return next;
    } else {
      return mid;
    }
  } else {
    return search(mid + 1, end);
  }
}
int main() {
  scanf("%I64d %I64d %I64d %I64d", &n, &k, &s, &t);
  for (long long i = 0; i < n; i++) {
    scanf("%I64d %I64d", &temp1, &temp2);
    if (cars[temp1] <= temp2) {
      cars[temp1] = temp2;
    }
    maxV = max(maxV, temp2);
  }
  stops.push_back(0);
  for (long long i = 0; i < k; i++) {
    scanf("%I64d", &temp1);
    stops.push_back(temp1);
  }
  stops.push_back(s);
  sort(stops.begin(), stops.end());
  long long maxD = 0;
  for (long long i = 1; i < stops.size(); i++) {
    temp1 = stops[i] - stops[i - 1];
    dis.push_back(temp1);
    maxD = max(temp1, maxD);
  }
  long long v = search(0, maxV);
  if (v == -1) {
    cout << -1;
    return 0;
  } else {
    v = max(maxD, v);
  }
  long long currentV = 0;
  for (auto i : cars) {
    if (i.second >= v) {
      cout << i.first;
      return 0;
    }
  }
  cout << -1;
}
