/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2020.06.07 15:48:36
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;

int main() {
    int n;cin >> n;
    vector<ll> d;
    for (int i = 0; i < n; i++) {
        ll t;cin >> t;
        d.push_back(t);
        d.push_back(-t);
    }
    sort(d.begin(), d.end());
    ll x,y;cin >> x >> y;
    x = abs(x) + abs(y);
    auto t = lower_bound(d.begin(), d.end(), x);
    if (t != d.end() && x == *t) {
        cout << 1 << endl;
        return 0;
    }
    for (int i = 0; i < d.size(); i++) {
        t = lower_bound(d.begin(), d.end(), x - d[i]);
        if (t != d.end() && x-d[i] == *t) {
            cout << 2 << endl;
            return 0;
        }
    }
    puts("-1");
    return 0;
}