#include <bits/stdc++.h>
using namespace std;

int n, x, y, t;
long long D;
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	cin >> n;
	vector<long long> d(n);
	for (int i = 0; i < n; ++i) cin >> d[i];
	sort(d.begin(), d.end());
	cin >> x >> y;
	D = abs(x) + abs(y);
	
	if (D==0) {
		cout << 0 << "\n";
		return 0;
	}
	if (binary_search(d.begin(), d.end(), D)) {
		cout << 1 << "\n";
		return 0;
	}
	for (int i = 0; i < n-1; ++i) {
		if (binary_search(d.begin()+i+1, d.end(), abs(D-d[i]))
						   || binary_search(d.begin()+i+1, d.end(), D+d[i])) {
			cout << 2 << "\n";
			return 0;
		}
	}
	cout << -1 << "\n";
}