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;
vector<vector<double> > cars;
vector<double> zapr;
double s;
double tf(double toplivo) {
  double time = 0;
  double len = zapr[0];
  double number = toplivo - len;
  if (number < 0) {
    return 1000000000;
  } else {
    if (number >= len) {
      time += len;
    } else {
      time += number + 2 * (len - number);
    }
  }
  for (int i = 1; i < zapr.size(); i++) {
    double len = zapr[i] - zapr[i - 1];
    double number = toplivo - len;
    if (number < 0) {
      return 1000000000;
    } else {
      if (number >= len) {
        time += len;
      } else {
        time += number + 2 * (len - number);
      }
    }
  }
  len = s - zapr[zapr.size() - 1];
  number = toplivo - len;
  if (number < 0) {
    return 1000000000;
  } else {
    if (number >= len) {
      time += len;
    } else {
      time += number + 2 * (len - number);
    }
  }
  return time;
}
int main() {
  std::ios::sync_with_stdio(false);
  double n, k, t, ci, vi;
  cin >> n >> k >> s >> t;
  for (int i = 0; i < n; i++) {
    cin >> ci >> vi;
    vector<double> help;
    help.push_back(ci);
    help.push_back(vi);
    cars.push_back(help);
  }
  for (int i = 0; i < k; i++) {
    cin >> ci;
    zapr.push_back(ci);
  }
  sort(zapr.begin(), zapr.end());
  int right = 1000000000;
  int left = 0;
  while (right - left > 1) {
    double m = (right + left) / 2;
    double result = tf(m);
    if (result > t) {
      left = m;
    } else {
      right = m;
    }
  }
  double bak = right;
  double answer = -1;
  for (int i = 0; i < n; i++) {
    double money = cars[i][0];
    double bak1 = cars[i][1];
    if (bak1 >= bak) {
      if (answer == -1) {
        answer = money;
      } else {
        answer = min(answer, money);
      }
    }
  }
  if (k > s) {
    cout << -1 << endl;
  } else {
    cout << answer << endl;
  }
  return 0;
}
