#include "iostream"
#include "climits"
#include "list"
#include "queue"
#include "stack"
#include "set"
#include "functional"
#include "algorithm"
#include "string"
#include "map"
#include "iomanip"
#include "cmath"

using namespace std;

const long long int MOD = 1000000007;

long long int N, M, K, H, W, L, R;


int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	cin >> N;
	vector<long long int>v(N);
	long long int om = -1;
	long long int em = 0;
	for (int i = 0; i < N; i++) {
		cin >> v[i];
		if (v[i] % 2) {
			om = max(om, v[i]);
		}
		else {
			em = max(em, v[i]);
		}
	}
	long long int a, b;
	cin >> a >> b;
	a = abs(a);
	b = abs(b);
	for (int i = 0; i < N; i++) {
		if (v[i] == a + b) {
			cout << "1\n";
			return 0;
		}
	}
	if ((a + b) % 2) {
		if (om + em >= a + b) {
			cout << "2\n";
			return 0;
		}
	}
	else {
		if (em * 2 >= a + b || om * 2 >= a + b) {
			cout << "2\n";
			return 0;
		}
	}
	cout << "-1\n";
	return 0;
}