import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.TreeSet;

public class Main {
	
	public static long MOD = 1000000007;
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int n = sc.nextInt();
		TreeSet<Long> set = new TreeSet<Long>();
		for(int i = 0; i < n; i++){ set.add(sc.nextLong()); }
		ArrayList<Long> arr = new ArrayList<>(set);
		
		final long x = sc.nextLong();
		final long y = sc.nextLong();
		final long d = Math.abs(x) + Math.abs(y);
		
		if(d == 0){
			System.out.println(0);
			return;
		}
		
		for(final long s : arr){
			if(d == s){
				System.out.println(1);
				return;
			}
		}
		
		for(int i = 0; i < arr.size(); i++){
			final long s = arr.get(i);
			
			{ // d = s1 + s2
				final long rest = Math.abs(d - s);
				final int pos = Collections.binarySearch(arr, rest);
				if(pos >= 0){
					System.out.println(2);
					return;
				}
			}
			{ // d = s1 - s2
				final long rest = Math.abs(s - d);
				final int pos = Collections.binarySearch(arr, rest);
				if(pos >= 0){
					System.out.println(2);
					return;
				}
			}
		}
		
		System.out.println(-1);
	}
}