#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll n,d[111111];

ll solve(ll x) {
  sort(d,d+n);
  if(!x) return 0;
  for(ll i=0; i<n; i++) {
    if(x==d[i]) return 1;
  }
  ll o=0,e=0;
  for(ll i=0; i<n; i++) {
    if(d[i]%2) o=d[i];
    else e=d[i];
    if(x%2&&abs(o-e)<=x&&x<=o+e) return 2;
  }
  if(x%2==0&&x<=d[n-1]*2) return 2;
  return -1;
}

int main() {
  ll x,y;
  cin >> n;
  for(ll i=0; i<n; i++) cin >> d[i];
  cin >> x >> y;
  cout << solve(abs(x)+abs(y)) << endl;
  return 0;
}