#include<iostream>
#include<iomanip>
#include<math.h>
#include<vector>
#include<algorithm>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<string>
#include<string.h>
#define INF 1000000000ll
#define MOD 1000000007ll
#define EPS 1e-10
#define REP(i,m) for(long long i=0; i<m; i++)
#define FOR(i,n,m) for(long long i=n; i<m; i++)
#define DUMP(a) for(long long dump=0; dump<(ll)a.size(); dump++) { cout<<a[dump]; if(dump!=(ll)a.size()-1) cout<<" "; else cout<<endl; }
#define ALL(v) v.begin(),v.end()
#define pb push_back
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
typedef long double ld;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	ll n;
	cin>>n;
	vector<ll> d(n);
	REP(i,n) cin>>d[i];
	ll x,y;
	cin>>x>>y;
	x=abs(x);
	y=abs(y);
	sort(ALL(d));
	if(x==0&&y==0) {
		cout<<0<<endl;
		return 0;
	}
	REP(i,n) {
		if(x+y==d[i]) {
			cout<<1<<endl;
			return 0;
		}
	}
	if(abs(x)+abs(y)<=2*d[n-1]) cout<<2<<endl;
	else cout<<-1<<endl;
}