#include <bits/stdc++.h>
using namespace std;

#define all(x) begin(x), end(x)
#ifdef CKISEKI
#define safe cerr << __PRETTY_FUNCTION__ << " line " << __LINE__ << "\n";
#define debug(a...) debug_(#a, a)
#define orange(a...) orange_(#a, a)
void debug_(auto s, auto ...a) {
  cerr << "\e[1;32m(" << s << ") = (";
  int f = 0;
  (..., (cerr << (f++ ? ", " : "") << a));
  cerr << ")\e[0m\n";
}
#include <experimental/iterator>
void orange_(auto s, auto L, auto R) {
  cerr << "\e[1;33m[ " << s << " ] = [ ";
  using namespace experimental;
  copy(L, R, make_ostream_joiner(cerr, ", "));
  cerr << " ]\e[0m\n";
}
#else
#define safe ((void)0)
#define debug(...) safe
#define orange(...) safe
#endif

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n, p, q, s;
  cin >> n >> p >> q >> s;
  multiset<int> a, b_;
  for (int i = 0; i < p; ++i) {
    int x;
    cin >> x;
    a.insert(x);
  }
  for (int i = 0; i < q; ++i) {
    int x;
    cin >> x;
    b_.insert(x);
  }
  
  auto valid = [&](int d) {
    auto b = b_;
    vector<pair<int, int>> v;
    for (auto ai : a) {
      v.emplace_back(min(ai + d, s - ai), ai - d);
    }
    ranges::sort(v);
    int c = n;
    for (auto [r, l] : v) {
      auto it = b.lower_bound(l);
      if (it == b.end())
        continue;
      if (*it > r)
        continue;
      b.erase(it);
      if (--c == 0)
        break;
    }
    return c == 0;
  };

  int L = -1, R = 1'000'000'000;
  if (not valid(R)) {
    cout << "-1\n";
    return 0;
  }

  while (R - L > 1) {
    int M = (L + R) >> 1;
    if (valid(M))
      R = M;
    else
      L = M;
  }
  cout << R << '\n';
  return 0;
}