import java.io.*;
import java.util.*;


class Main {
    public static void main(String[] args) {
        MyScanner sc = new MyScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));
        int n=sc.nextInt();
        long[]d=new long[n];
        long[]a=new long[n],b=new long[n];
        int p=0,q=0;
        Set<Long>hs=new HashSet<Long>();
        long e=-1,o=-1;
        for(int i=0;i<n;++i){
            d[i]=sc.nextLong();hs.add(d[i]);
            if(d[i]%2==1){
                o=Math.max(o,d[i]);
                b[q++]=d[i];
            }else{
                e=Math.max(e,d[i]);
                a[p++]=d[i];
            }
        }
        Arrays.sort(a,0,p);
        Arrays.sort(b,0,q);
        long x=sc.nextLong(),y=sc.nextLong();
        long dd=Math.abs(x)+Math.abs(y);
        if(dd==0){
            out.println(0);
            out.close();
            return;
        }
        if(hs.contains(dd)){
            out.println(1);
            out.close();
            return;
        }
        if(dd%2==0){
            if(dd<=2*e||dd<=2*o)
                out.println(2);
            else
                out.println(-1);
        }else{
            if(e<0||o<0){
                out.println(-1);
                out.close();
                return;
            }
            boolean ok=false;
            for(long xx:Arrays.copyOf(a,p)){
                int l=Arrays.binarySearch(b,0,q,Math.abs(dd-xx)-1);
                if(l<0)l=-l-1;
                int r=Arrays.binarySearch(b,0,q,dd+xx+1);
                if(r<0)r=-r-1;
                if(l<r){
                    ok=true;
                    break;
                }
            }
            for(long xx:Arrays.copyOf(b,q)){
                int l=Arrays.binarySearch(a,0,p,Math.abs(dd-xx)-1);
                if(l<0)l=-l-1;
                int r=Arrays.binarySearch(a,0,p,dd+xx+1);
                if(r<0)r=-r-1;
                if(l<r){
                    ok=true;
                    break;
                }
            }
            out.println(ok?2:-1);
        }
        out.close();
    }
    // http://codeforces.com/blog/entry/7018
    //-----------PrintWriter for faster output---------------------------------
    public static PrintWriter out;
    //-----------MyScanner class for faster input----------
    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;
        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
        int nextInt() {
            return Integer.parseInt(next());
        }
        long nextLong() {
            return Long.parseLong(next());
        }
        double nextDouble() {
            return Double.parseDouble(next());
        }
        String nextLine(){
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
}