#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <fstream>
#include <set>
#include <utility>
#include <algorithm>
#include <queue>
#include <stack>
#include <deque>
#include <numeric>
#include <sstream>
#include <list>
#include <map>
#include <stdlib.h>
#include <time.h>

#define rep(i,p,n) for(int i=(int)p;i<(int)n;i++)
#define repp(i,p,n) for(int i=(int)p;i>=(int)n;i--)
#define Sort(x) sort(x.begin(),x.end());
#define ll long long
#define INF 2000000000

using namespace std;

int main() {
	int n;
	cin >> n;

	vector<ll> v(n);
	rep(i, 0, n)cin >> v[i];
	Sort(v);
	ll x, y;
	cin >> x >> y;

	if (x == 0 && y == 0) {
		cout << 0 << endl;
		return 0;
	}
	else {
		ll dis = abs(x) + abs(y);
		rep(i, 0, n) {
			if (dis == v[i]) {
				cout << 1 << endl;
				return 0;
			}
		}
		rep(i, 0, n) {
			rep(j, 0, n) {
				if (dis == v[i] + v[j]) {
					cout << 2 << endl;
					return 0;
				}
			}
		}
		cout << -1 << endl;
		
	}

	
	
	return 0;
}