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

ll d[100000];

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
#ifdef LOCAL
	std::ifstream in("in");
	std::cin.rdbuf(in.rdbuf());
#endif

	int N;
	cin >> N;
	set<ll> s;
	for(int i = 0; i < N; i++){
		cin >> d[i];
		s.insert(d[i]);
	}
	sort(d, d + N);

	ll x, y;
	cin >> x >> y;
	ll D = max(abs(x), abs(y));

	if(D == 0){
		cout << 0 << endl;
		return 0;
	}
	if(s.count(abs(x) + abs(y))){
		cout << 1 << endl;
		return 0;
	}
	for(int i = 0; i < N; i++){
		int r = upper_bound(d, d + N, D + d[i]) - d;
		int l = lower_bound(d, d + N, abs(D - d[i])) - d;
		if(r - l >= 1){
			cout << 2 << endl;
			return 0;
		}
	}
	cout << -1 << endl;

}