using System;
using System.Linq;

public class Program
{
    static void Main()
    {
        string s = Console.ReadLine();
        int N = int.Parse(s);

        s = Console.ReadLine();
        var t = s.Split(' ');
        var D = new int[N];
        for (int i = 0; i < N; ++i) {
            D[i] = int.Parse(t[i]);
        }
        Array.Sort(D);

        s = Console.ReadLine();
        t = s.Split(' ');

        int x = int.Parse(t[0]);
        int y = int.Parse(t[1]);

        int X = Math.Abs(x + y);
        int Y = Math.Abs(x - y);
        int M = Math.Max(X, Y);

        if (D.Contains(M)) {
            Console.WriteLine(1);
            return;
        } 

        for (int i = 0; i < N; ++i) {        
            int hi = N;
            int lo = 0;
            while (hi - lo > 1) {
                int mid = (hi + lo) / 2;
                if (D[mid] <= M + D[i]) {
                    lo = mid;
                } else {
                    hi = mid;
                }
            }

            if (lo == i) {
                lo += 1;
            }

            if (lo < N && D[lo] <= M + D[i] && D[lo] >= M - D[i]) {
                Console.WriteLine(2);
                return;
            }
        }

        Console.WriteLine(-1);
    }
}