#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
using namespace std;
typedef long long int ll;
const ll N = 100000;
ll d[N],n,cp,src[2][N],lst[2];

int main() {
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		scanf("%d", d + i);
		src[d[i] % 2][lst[d[i] % 2]] = d[i];
		lst[d[i] % 2]++;
	}
	sort(d , d + n);
	ll x, y; cin >> x >> y;
	cp = abs(x) + abs(y);
	if (cp == 0) { cout << 0 << endl; goto end; }
	if (find(d, d + n, cp) - d < n) { cout << 1 << endl; goto end; }
	for (int i = 0; i < n; i++) {
		ll lb = abs(cp - d[i]), ub = (cp + d[i]);
		ll ni = lower_bound(src[lb % 2], src[lb % 2] + lst[lb % 2], lb) - src[lb % 2];
		if (ni<lst[lb%2]&&src[lb%2][ni] <= ub)
		{ cout << 2 << endl; goto end; }
	}
	cout << -1 << endl;
end:;
	return 0;
}