#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main() {
    int n; cin >> n;
    vector<int> d(n);
    for (int &di: d) cin >> di;
    sort(d.begin(), d.end());
    int x, y; cin >> x >> y;
    int dist = abs(x) + abs(y);
    int res = dist == 0 ? 0 : 3;
    vector<int> ma{0, 0};
    for (int i = 0; i < n; i++) {
        if (d[i] == dist) res = min(res, 1);
        ma[d[i] % 2] = d[i];
        if (abs(x - d[i]) <= ma[abs(x - d[i]) % 2]) res = min(res, 2);
    }
    if (res == 3) {
        cout << -1 << endl;
    } else {
        cout << res << endl;
    }
    return 0;
}