1 1 2 2
1000000000 1000000000
1
 1 1 1000000000 1000000000
100 1000000000
1
 1 1 10 18
5 6
5
 2 1 1000000000 2000000000
111 999999999
101 999999998
1
 4 13 400 600
13 30
1 19
1 160
1 113
58 73 15 319 194 362 128 157 336 162 77 90 96
 1 15 100 200
283 8
30 58 16 45 80 82 55 95 24 23 86 28 51 47 20
 3 2 300 400
24 68
13 65
15 113
127 177
 1 1 2 1
1 10
1
 4 2 7 15
10 9
4 4
9 3
4 10
1 6
 2 1 1000000000 2000000000
111 1000000000
101 1000000000
5
 2 1 1000000000 2000000000
111 999999998
101 999999998
1
 1 1 1000000000 1000000000
1 1000000000
1

1000000000
 -1
 5
 111
 1
 -1
 -1
 -1
 4
 101
 -1
 -1

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6 + 100;
const int INF = 1e9 + 9;
const double eps = 1e-7;
vector<int> zap(2e5 + 5, 0);
long long s, k, t;
bool cmpbin(pair<long long, long long> a, long long b) {
  if (3 * s - (k + 1) * a.second >= t)
    return 1;
  else
    return 0;
}
bool cmp(pair<long long, long long> a, pair<long long, long long> b) {
  if (b.second != a.second) {
    return a.second < b.second;
  } else
    return a.first < b.first;
}
int main() {
  long long n;
  cin >> n >> k >> s >> t;
  vector<pair<long long, long long> > v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i].first >> v[i].second;
  }
  for (int i = 0; i < k; i++) {
    cin >> zap[i];
  }
  sort(v.begin(), v.end(), cmp);
  int u = lower_bound(v.begin(), v.end(), 1, cmpbin) - v.begin();
  if (u < v.size()) {
    if (3 * s - (k + 1) * v[u].second <= t) {
      long long mn = v[u].first;
      for (int i = u; i < v.size(); i++) {
        mn = min(mn, v[i].first);
      }
      cout << mn;
    } else
      cout << -1;
  } else
    cout << -1;
  return 0;
}
