#include <bits/stdc++.h>

using namespace std;

using ll = long long;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    set<ll> s;
    for (int i = 0; i < n; i++) {
        ll d;
        cin >> d;
        s.insert(d);
    }
    ll x, y;
    cin >> x >> y;
    ll dist = abs(x) + abs(y);
    int ans = -1;
    if (dist == 0) {
        ans = 0;
    } else if (s.find(dist) != s.end()) {
        ans = 1;
    } else {
        for (ll v : s) {
            if (s.find(dist - v) != s.end()) ans = 2;
            if (s.find(v + dist) != s.end()) ans = 2;
        }

        set<ll> s2, s3;
        for (ll v : s) {
            if (v >= abs(x)) s2.insert(v - abs(x));
            if (v >= abs(y)) s3.insert(v - abs(y));
        }
        for (ll v : s2) {
            if (s3.find(v) != s3.end()) ans = 2;
        }
    }
    cout << ans << endl;
    return 0;
}