#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
 
using namespace std;
using namespace __gnu_pbds;
 
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define fbo find_by_order
#define ook order_of_key
 
typedef long long ll;
typedef pair<ll,ll> ii;
typedef vector<int> vi;
typedef long double ld; 
typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> pbds;
typedef set<ll>::iterator sit;
typedef map<ll,ll>::iterator mit;

ll mx[2];
ll a[111111];

int main()
{
	ios_base::sync_with_stdio(0); cin.tie(0);
	int n; cin>>n;
	mx[0]=-ll(1e9); mx[1]=-ll(1e9);
	for(int i=0;i<n;i++)
	{
		cin>>a[i];
		mx[a[i]&1]=max(mx[a[i]&1],a[i]);
	}
	ll x,y; cin>>x>>y;
	ll D = abs(x)+abs(y);
	if(D==0){cout<<0<<'\n'; return 0;}
	for(int i=0;i<n;i++)
	{
		if(a[i]==D){cout<<1<<'\n'; return 0;}
	}
	ll mxodd=mx[0]+mx[1];
	ll mxeven=max(mx[0]*2,mx[1]*2);
	if(D&1)
	{
		cout<<(D<=mxodd?2:-1)<<'\n';
	}
	else
	{
		cout<<(D<=mxeven?2:-1)<<'\n';
	}
}