#include<bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> PII;

const int MM = 1e9 + 7;
const double eps = 1e-8;
const int MAXN = 2e6 + 10;

int n, m;

void prework(){

}

void read(){

}

int a[MAXN];

void solve(int casi){
//	cout << "Case #" << casi << ": ";
	cin >> n;
	int x, y;
	for (int i = 1; i <= n; i++)
		cin >> a[i];
	cin >> x >> y;
	if (x == 0 && y == 0){
		cout << 0 << endl;
		return ;
	}
	int flag = 0;
	for (int i = 1; i <= n; i++)
		if (abs(x) + abs(y) == a[i])
			flag = 1;
	if (flag == 1){
		cout << 1 << endl;
		return ;
	}
	int odd = -1, eve = -2;
	sort(a + 1, a + n + 1);
	for (int i = 1; i <= n; i++){
		int del = abs(abs(x) + abs(y) - a[i]);
		if (del & 1){
			if (odd >= del)
				flag = 1;
		}
		else{
			if (eve >= del)
				flag = 1;
		}
		if (a[i] & 1) odd = a[i];
		else eve = a[i];
	}
	if (flag)
		cout << 2 << endl;
	else
		cout << -1 << endl;
}

void printans(){

}


int main(){
	std::ios::sync_with_stdio(false);
	prework();
	int T = 1;
//	cin>>T;
	for(int i = 1; i <= T; i++){
		read();
		solve(i);
		printans();
	}
	return 0;
}