#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<ll, ll> p_ll;

template<class T>
void debug(T itr1, T itr2) { auto now = itr1; while(now<itr2) { cout << *now << " "; now++; } cout << endl; }
#define repr(i,from,to) for (ll i=(ll)from; i<(ll)to; i++)
#define all(vec) vec.begin(), vec.end()
#define rep(i,N) repr(i,0,N)
#define per(i,N) for (int i=(int)N-1; i>=0; i--)

const ll MOD = pow(10,9)+7;
const ll LLINF = pow(2,61)-1;
const int INF = pow(2,30)-1;

vector<ll> fac;
void c_fac(int x=pow(10,6)+10) { fac.resize(x,true); rep(i,x) fac[i] = i ? (fac[i-1]*i)%MOD : 1; }
ll inv(ll a, ll m=MOD) { ll b = m, x = 1, y = 0; while (b!=0) { int d = a/b; a -= b*d; swap(a,b); x -= y*d; swap(x,y); } return (x+m)%m; }
ll nck(ll n, ll k) { return fac[n]*inv(fac[k]*fac[n-k]%MOD)%MOD; }
ll gcd(ll a, ll b) { if (a<b) swap(a,b); return b==0 ? a : gcd(b, a%b); }
ll lcm(ll a, ll b) { return a/gcd(a,b)*b; }


int main() {
  ll n; cin >> n;
  ll d[n]; rep(i,n) cin >> d[i]; sort(d,d+n);
  ll x, y; cin >> x >> y;
  ll to = abs(x)+abs(y);
  
  set<ll> o, e; rep(i,n) { if (d[i]%2) o.insert(d[i]); else e.insert(d[i]); }

  ll result = -1;
  if (to==0) result = 0;
  else if (o.count(to)||e.count(to)) result = 1;
  else {
    if (to%2) {
      if (o.size()&&e.size()) {
        if (*o.rbegin()+*e.rbegin()>=to) result = 2;
      }
    }
    else {
      ll md = 0;
      if (o.size()) md = max(md, *o.rbegin()*2);
      if (e.size()) md = max(md, *e.rbegin()*2);
      if (md>=to) result = 2;
    }
  }
  cout << result << endl;
  return 0;
}