#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;
  Int u=abs(x+y),v=abs(x-y);
  if(u<v) swap(u,v);
  sort(d.begin(),d.end());
  for(Int i=0;i<n;i++){
    if(d[i]==u){
      cout<<1<<endl;
      return 0;      
    }
  }
  for(Int i=0;i<n;i++){
    Int k=lower_bound(d.begin(),d.end(),u-d[i])-d.begin();
    if(k<n&&u-d[i]<=d[k]&&d[k]<=u+d[i]){
      cout<<2<<endl;
      return 0;
    }
  }
  cout<<-1<<endl;
  return 0;
}