#include <bits/stdc++.h>
using namespace std;
int main() {
  cin.tie(0);
  cout.tie(0);
  ios_base::sync_with_stdio(0);
  long long n, k, s, t;
  cin >> n >> k >> s >> t;
  vector<long long> c(n), v(n), g(k + 1, 1e9 + 5), f(k + 2, 0);
  for (int i = 0; i < n; i++) cin >> c[i] >> v[i];
  for (int i = 0; i < k; i++) cin >> g[i];
  sort(g.begin(), g.end());
  g[k] = s;
  for (int i = k - 1; i >= 0; i--) g[i + 1] -= g[i];
  sort(g.begin(), g.end());
  for (int i = 1; i <= k + 1; i++) f[i] = f[i - 1] + g[i - 1];
  long long ret = -1;
  for (int i = 0; i < n; i++)
    if (g[k] <= v[i]) {
      long long x = upper_bound(g.begin(), g.end(), v[i] / 2) - g.begin();
      if (2 * s - f[x] - (k + 1 - x) * v[i] + (f[k + 1] - f[x]) <= t) {
        if (ret == -1)
          ret = c[i];
        else
          ret = min(ret, c[i]);
      }
    }
  cout << ret << endl;
  return 0;
}
