#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-8;
const ll mod=1e9+7;
const int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};

int n,x,y;
vi a,b[2];

int main(){
	cin>>n;
	a=vi(n);
	for(int i=0;i<n;i++){
		int t;
		cin>>t;
		a[i]=t;
		b[t%2].push_back(t);
	}
	cin>>x>>y;
	x=abs(x+y);
	sort(b[0].rbegin(),b[0].rend());
	sort(b[1].rbegin(),b[1].rend());
	for(int i=0;i<n;i++) if(x==a[i]){
		cout<<1<<endl;
		return 0;
	}
	for(int i=0;i<4;i++) if((i/2+i%2+x)%2==0){
		int I=i/2,J=i%2,t=-1,B=(I==J?1:0);
		if(b[I].size()>0){
			t=b[I][0];
			if(b[J].size()>B) t+=b[J][B];
		}
		if(t>=x){
			cout<<2<<endl;
			return 0;
		}
	}
	cout<<-1<<endl;
}