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

int n, x, y, t, r=3;
long long a;
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;
	a = abs(x) + abs(y);
	if (a==0) {
		printf("0\n");
		return 0;
	}
	
	for (int i = 0; i < n; ++i) {
		if (d[i]==a) r = 1;
		else if (i<n-1 && (binary_search(d.begin()+i+1, d.end(), abs(a-d[i]))
						   || binary_search(d.begin()+i+1, d.end(), a+d[i])))
			if (r==3) r = 2;
	}
	if (r==3) r = -1;
	cout << r << "\n";
}