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;
template <typename T>
inline T maxer(T &a, T b) {
  a = max(a, b);
}
template <typename T>
inline T miner(T &a, T b) {
  a = min(a, b);
}
void inline iOS() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
}
void inline fin() { freopen("in", "r", stdin); }
void inline fout() { freopen("out", "w", stdout); }
const int inf = ~0u / 10;
const long long linf = ~0ull / 20;
const int maxn = 2e5 + 20;
;
int g[maxn];
pair<int, int> q[maxn];
int n, m, s, t;
int get(int f) {
  int res = 0;
  for (int i = 1; res < inf && i < m; i++) {
    int dis = g[i] - g[i - 1];
    if (dis > f) return inf;
    res += dis * 2 - min(dis, f - dis);
  }
  return res;
}
int main() {
  iOS();
  cin >> n >> m >> s >> t;
  for (int i = 0; i < n; i++) cin >> q[i].first >> q[i].second;
  for (int i = 0; i < m; i++) cin >> g[i];
  g[m++] = 0;
  g[m++] = s;
  sort(g, g + m);
  int ans = -1, st = 1, en = 1e9;
  while (st <= en) {
    int mid = (st + en) / 2, mx = 0;
    for (int i = 0; i < n; i++)
      if (q[i].first <= mid) maxer(mx, q[i].second);
    if (get(mx) <= t)
      ans = mid, en = mid - 1;
    else
      st = mid + 1;
  }
  cout << ans << '\n';
  return 0;
}
