#include <bits/stdc++.h>

using namespace std;

const int MAX = 1e5 + 10;
int n;
long long d[MAX];
long long x, y;

int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%lld", d + i);
  }
  scanf("%lld%lld", &x, &y);
  sort(d, d + n);
  if (x == 0 && y == 0) {
    cout << 0 << endl;
    return 0;
  }
  x = llabs(x);
  y = llabs(y);
  for (int i = 0; i < n; i++) {
    if (d[i] == x + y) {
      cout << 1 << endl;
      return 0;
    }
  }

  vector<long long> vv[2];
  for (int i = 0; i < n; i++) {
    vv[d[i] % 2].emplace_back(d[i]);
  }
  // if (d[i] + d[j] >= x + y && (d[i] + d[j] - (x + y)) % 2 == 0) ok?
  for (int i = 0; i < n; i++) {
    if (d[i] + vv[d[i] % 2].back() >= x + y && (d[i] + vv[d[i] % 2].back() - (x + y)) % 2 == 0) {
      cout << 2 << endl;
      return 0;
    }
  }

  cout << -1 << endl;
}