#include<iostream>
#include<algorithm>
#include<set>
using namespace std;
int N;
int D[1<<17];
int x,y;
main()
{
	cin>>N;
	set<int>S[2];
	for(int i=0;i<N;i++)
	{
		cin>>D[i];
		S[D[i]%2].insert(D[i]);
	}
	cin>>x>>y;
	x=abs(x);
	y=abs(y);
	if(x==0&&y==0)
	{
		cout<<0<<endl;
		return 0;
	}
	int ans=-1;
	for(int i=0;i<N;i++)
	{
		int L=abs(x+y-D[i]),R=max(abs(D[i]-x)+y,abs(D[i]-y)+x);
		set<int>::iterator it=S[L%2].lower_bound(L);
		if(it!=S[L%2].end()&&*it<=R)ans=2;
		if(L==0)
		{
			cout<<1<<endl;
			return 0;
		}
	}
	cout<<ans<<endl;
}