#include<bits/stdc++.h>

using namespace std;

int main()
{
  int N, D[100000], X, Y;

  cin >> N;
  for(int i = 0; i < N; i++) {
    cin >> D[i];
  }
  cin >> X >> Y;

  X = abs(X) + abs(Y);

  if(X == 0) {
    cout << 0 << endl;
  } else {
    int odd = 0, even = 0;
    int ret = -1;
    sort(D, D + N);
    for(int i = 0; i < N; i++) {
      if(D[i] == X) {
        ret = 1;
        break;
      }
      if(D[i] % 2 == 0) even = D[i];
      else odd = D[i];
      int rest = abs(X - D[i]);
      if(rest % 2 == 0) {
        if(rest <= even) ret = 2;
      } else {
        if(rest <= odd) ret = 2;
      }
    }
    cout << ret << endl;
  }

  return (0);
}