#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  vector<Int> d(n);
  for(Int i=0;i<n;i++) cin>>d[i];
  Int x,y;
  cin>>x>>y;
  if(x==0&&y==0){
    cout<<0<<endl;
    return 0;
  }
  Int s=abs(x)+abs(y);
  sort(d.begin(),d.end());
  for(Int i=0;i<n;i++){
    if(d[i]==s){
      cout<<1<<endl;
      return 0;      
    }
  }
  Int e=-1,o=-1;
  for(Int i=0;i<n;i++){
    if(d[i]&1) chmax(o,d[i]);
    else chmax(e,d[i]);
    
    if(~e){
      Int t=d[i]+e,w=abs(d[i]-e);
      if(((t&1)==(s&1))&&w<=s&&s<=t){
        cout<<2<<endl;
        return 0;
      }
    }
    if(~o){
      Int t=d[i]+o,w=abs(d[i]-o);
      if(((t&1)==(s&1))&&w<=s&&s<=t){
        cout<<2<<endl;
        return 0;
      }
    }
  }
  cout<<-1<<endl;
  return 0;
}