#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

int main() {
  int n;
  cin >> n;

  vector<int> d(n);
  vector<int> even, odd;
  for (int i = 0; i < n; i++) {
    cin >> d[i];
    if (d[i] % 2 == 0) {
      even.push_back(d[i]);
    } else {
      odd.push_back(d[i]);
    }
  }

  int x, y;
  cin >> x >> y;

  if (x == 0 && y == 0) {
    cout << 0 << endl;
    return 0;
  }

  int dist = abs(x) + abs(y);

  for (int i = 0; i < n; i++) {
    if (dist == d[i]) {
      cout << 1 << endl;
      return 0;
    }
  }

  if (dist % 2 == 0) {
    for (int i = 0; i < n; i++) {
      if (dist <= d[i] * 2) {
        cout << 2 << endl;
        return 0;
      }
    }
    cout << -1 << endl;
    return 0;
  }

  sort(even.begin(), even.end());
  sort(odd.begin(), odd.end());

  for (int i = 0; i < even.size(); i++) {
    auto it = lower_bound(odd.begin(), odd.end(), even[i]);
    if (it != odd.begin()) {
      int j = it - odd.begin() - 1;
      if (even[i] - odd[j] <= dist && dist <= even[i] + odd[j]) {
        cout << 2 << endl;
        return 0;
      }
    }
  }
  for (int i = 0; i < odd.size(); i++) {
    auto it = lower_bound(even.begin(), even.end(), odd[i]);
    if (it != even.begin()) {
      int j = it - even.begin() - 1;
      if (odd[i] - even[j] <= dist && dist <= odd[i] + even[j]) {
        cout << 2 << endl;
        return 0;
      }
    }
  }

  cout << -1 << endl;
}