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

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