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

#define INF 1.1e9
#define LINF 1.1e18
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(), (v).end()
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define BIT(x,n) bitset<n>(x)
#define PI 3.14159265358979323846

typedef long long ll;
typedef pair<int,int> P;
typedef pair<int,P> PP;

struct edge {
	int to, cost;
	edge(int t,int c):to(t),cost(c) {}
};

int dx[]={1,-1,0,0},dy[]={0,0,1,-1};
int ddx[]={1,1,1,0,-1,-1,-1,0},ddy[]={1,0,-1,-1,-1,0,1,1};

ll mypow(ll x,ll n,ll m) {	//xのn乗をmで割った余り
	if(n==0) return 1;
	if(n%2==0) return mypow(x*x%m,n/2,m);
	else return x*mypow(x,n-1,m)%m;
}

//-----------------------------------------------------------------------------

int n,x,y;
vector<ll> A,B;

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

	cin>>n;
	ll d[n];
	REP(i,n) {
		cin>>d[i];
		if(d[i]&1) B.pb(d[i]);
		else A.pb(d[i]);
	}
	cin>>x>>y;
	ll z=abs(x)+abs(y);
	if(z==0) {
		cout<<0<<endl;
		return 0;
	}
	A.pb(LINF),B.pb(LINF);
	sort(ALL(A));sort(ALL(B));sort(d,d+n);
	if(find(d,d+n,z)!=d+n) {
		cout<<1<<endl;
		return 0;
	}
	if(z&1) {
		ll odd=-1,even=-1;
		REP(i,n) {
			if(d[i]&1) odd=d[i];
			else even=d[i];
			if(even==-1||odd==-1) continue;
			if(abs(odd-even)<=z&&z<=odd+even) {
				cout<<2<<endl;
				return 0;
			}
		}
	}
	else {
		if(2*d[n-1]>=z) {
			cout<<2<<endl;
			return 0;
		}
	}
	cout<<-1<<endl;

	return 0;
}