#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;

int main()
{
    int n; ll x, y;
    cin>>n;
    ll d[100010];
    vector<ll> d0, d1;
    for(int i=0; i<n; i++){
        cin>>d[i];
        if(d[i]&1) d1.push_back(d[i]);
        else d0.push_back(d[i]);
    }
    cin>>x>>y;
    ll s=abs(x)+abs(y);
    if(s==0){
        cout<<0<<endl;
        return 0;
    }
    for(int i=0; i<n; i++){
        if(s==d[i]){
            cout<<1<<endl;
            return 0;
        }
    }
    sort(d0.begin(), d0.end());
    sort(d1.begin(), d1.end());
    ll mx0=(d0.empty() ? 0 : d0.back());
    ll mx1=(d1.empty() ? 0 : d1.back());
    if(s%2==0){
        if(s<=2*max(mx0, mx1)) cout<<2<<endl;
        else cout<<-1<<endl;
    }else{
        if(d0.empty() || d1.empty()){
            cout<<-1<<endl;
            return 0;
        }
        for(auto a:d0){
            int i=lower_bound(d1.begin(), d1.end(), abs(a-s))-d1.begin();
            if(i<d1.size() && d1[i]<=a+s){
                cout<<2<<endl;
                return 0;
            }
        }
        cout<<-1<<endl;
    }
    return 0;
}