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;
int n, k, s, t, needed = 0;
vector<long long> v;
bool ok(long long mid, long long g[]) {
  long long c = needed, mn = 0;
  for (int i = 1; i < k; i++) c -= max(mid - g[i] - g[i - 1], mn);
  return (c <= 0);
}
int main() {
  cin >> n >> k >> s >> t;
  k += 2;
  int c[n];
  long long g[k], mn = 0;
  map<long long, int> price;
  v.resize(n);
  for (int i = 0; i < n; i++) {
    scanf("%d %lld", &c[i], &v[i]);
    price[v[i]] = c[i];
  }
  sort(v.begin(), v.end());
  g[0] = 0, g[k - 1] = s;
  for (int i = 1; i < k - 1; i++) scanf("%lld", &g[i]);
  sort(g, g + k);
  for (int i = 1; i < k; i++) mn = max(mn, g[i] - g[i - 1]);
  if ((s * 2) - t > 0) needed = (s * 2) - t;
  long long l = mn, r = 1e10, mid;
  while (l < r - 1) {
    mid = (l + r) / 2;
    if (ok(mid, g))
      r = mid;
    else
      l = mid;
  }
  vector<long long>::iterator low;
  low = lower_bound(v.begin(), v.end(), l);
  int i = low - v.begin();
  if (i == v.size())
    cout << -1;
  else {
    int ans = price[v[i]];
    for (i; i < n; i++) ans = min(ans, price[v[i]]);
    cout << ans;
  }
}
