using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var d = NList;
        var c = NList;
        WriteLine(Game(n, d, Math.Abs(c[0]) + Math.Abs(c[1])));
    }
    static int Game(int n, int[] d, long x)
    {
        if (x == 0)
        {
            return 0;
        }
        var emax = -1;
        var omax = -1;
        var elist = new List<long>();
        var olist = new List<long>();
        foreach (var di in d)
        {
            if (x == di)
            {
                return 1;
            }
            if (di % 2 == 0)
            {
                emax = Math.Max(emax, di * 2);
                elist.Add(di);
            }
            else
            {
                omax = Math.Max(omax, di * 2);
                olist.Add(di);
            }
        }
        if (x % 2 == 0) return x <= emax || x <= omax ? 2 : -1;
        else
        {
            if (elist.Count == 0 || olist.Count == 0)
            {
                return -1;
            }
            elist.Sort();
            olist.Sort();
            foreach (var e in elist)
            {
                var opos = Math.Max(LowerBound(0, e, olist), LowerBound(0, x - e, olist));
                if (opos < olist.Count && olist[opos] <= x + e)
                {
                    return 2;
                }
            }
            foreach (var o in olist)
            {
                var epos = Math.Max(LowerBound(0, o, elist), LowerBound(0, x - o, elist));
                if (epos < elist.Count && elist[epos] <= x + o)
                {
                    return 2;
                }
            }
            return -1;
        }
    }
    static int LowerBound(int left, long min, IList<long> list)
    {
        if (list[left] >= min) return left;
        var ng = left;
        var ok = list.Count;
        while (ok - ng > 1)
        {
            var mid = (ng + ok) / 2;
            if (list[mid] < min) ng = mid;
            else ok = mid;
        }
        return ok;
    }
}