#include <bits/stdc++.h>

#define VARNAME(x) #x
#define show(x) cerr << #x << " = " << x << endl

using namespace std;
using ll = long long;

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz:" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = (ll)1e9 + 7LL;

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 64;

int main()
{
    int N;
    cin >> N;
    vector<ll> d(N);
    vector<ll> odd;
    vector<ll> even;
    for (int i = 0; i < N; i++) {
        cin >> d[i];
        ((d[i] % 2 == 0) ? even : odd).push_back(d[i]);
    }
    ll x, y;
    cin >> x >> y;
    const ll dist = abs(x) + abs(y);
    const ll maxi = *max_element(d.begin(), d.end());
    if (dist == 0) {
        cout << 0 << endl;
        return 0;
    }
    for (int i = 0; i < N; i++) {
        if (d[i] == dist) {
            cout << 1 << endl;
            return 0;
        }
    }
    if (dist > maxi * 2) {
        cout << -1 << endl;
    } else if (dist % 2 == 0) {
        cout << 2 << endl;
    } else if (even.empty() or odd.empty()) {
        cout << -1 << endl;
    } else {
        const ll oddmaxi = *max_element(odd.begin(), odd.end());
        const ll evenmaxi = *max_element(even.begin(), even.end());
        if (dist >= abs(oddmaxi - evenmaxi) and dist <= oddmaxi + evenmaxi) {
            cout << 2 << endl;
        } else {
            cout << -1 << endl;
        }
    }

    return 0;
}