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 void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int n = sc.nextInt();
		long[] array = new long[n];
		
		long odd_max = 0, even_max = 0;
		for(int i = 0; i < n; i++){
			array[i] = sc.nextLong();
			
			if(array[i] % 2 == 0){
				even_max = Math.max(even_max, array[i]);
			}else{
				odd_max = Math.max(odd_max, array[i]);
			}
		}
		
		final long d_odd_max = even_max + odd_max;
		final long d_even_max = Math.max(odd_max * 2, even_max * 2);
		
		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 : array){
			if(s == d){
				System.out.println(1);
				return;
			}
		}
		
		if(d % 2 == 0 && d <= d_even_max - 2){
			System.out.println(2);
			return;
		}
		if(d % 2 == 1 && d <= d_odd_max - 2){
			System.out.println(2);
			return;
		}
		
		System.out.println(-1);
	}
}