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 N = 2e5 + 3;
const double OO = 2e10;
int n, k, s, t;
pair<int, int> p[N];
int g[N];
vector<pair<int, int>> good;
double det(double a, double b, double c, double d) { return a * d - b * c; }
double solve(double d, double l) {
  double t = OO;
  double t1, t2;
  t1 = 0;
  t2 = 2 * (d - t1);
  if (0 <= t2 && 2 * t1 + 0.5 * t2 <= l) {
    t = min(t, t1 + t2);
  }
  t2 = 0;
  t1 = d - 0.5 * t2;
  if (0 <= t1 && 2 * t1 + 0.5 * t2 <= l) {
    t = min(t, t1 + t2);
  }
  double D = det(1, 0.5, 2, 0.5);
  t1 = det(d, 0.5, l, 0.5) / D;
  t2 = det(1, d, 2, l) / D;
  if (0 <= t1 && 0 <= t2 && 2 * t1 + 0.5 * t2 <= l) {
    t = min(t, t1 + t2);
  }
  return t;
}
bool check(int m) {
  int l = good[m].second;
  double T = 0;
  for (int(i) = (0); !((i) == (k + 1)); (k + 1) > (0) ? (i)++ : (i)--) {
    int from = i == 0 ? 0 : g[i - 1];
    int to = i == k ? s : g[i];
    T += solve(to - from, l);
    if (T >= OO) return false;
  }
  return T <= t;
}
int main(int argc, char* argv[]) {
  ios::sync_with_stdio(0);
  cin >> n >> k >> s >> t;
  for (int(i) = (0); !((i) == (n)); (n) > (0) ? (i)++ : (i)--) {
    int a, b;
    cin >> a >> b;
    p[i] = make_pair(a, b);
  }
  for (int(i) = (0); !((i) == (k)); (k) > (0) ? (i)++ : (i)--) {
    cin >> g[i];
  }
  sort(g, g + k);
  sort(p, p + n);
  for (int(i) = (0); !((i) == (n)); (n) > (0) ? (i)++ : (i)--) {
    if (good.size() == 0 || p[i].second > good.back().second) {
      good.push_back(p[i]);
    }
  }
  int l = 0, r = good.size() - 1;
  for (; l < r;) {
    int m = (l + r) / 2;
    if (check(m))
      r = m;
    else
      l = m + 1;
  }
  if (check(l)) {
    cout << -1 << endl;
  } else {
    cout << good[l].first << endl;
  }
  return 0;
}
