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];
		
		for(int i = 0; i < n; i++){
			array[i] = sc.nextLong();
		}
		
		TreeSet<Long> odds = new TreeSet<Long>();
		TreeSet<Long> evens = new TreeSet<Long>();
		for(int i = 0; i < n; i++){
			if(array[i] % 2 == 0){
				evens.add(array[i]);
			}else{
				odds.add(array[i]);
			}
		}
		
		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;
		}
		
		if(d % 2 == 0){
			if(evens.ceiling(d) != null){
				System.out.println(1);
				return;
			}
			
			for(final long s : evens){
				final long diff = Math.abs(d - s);
				
				if(evens.ceiling(diff) != null){
					System.out.println(2);
					return;
				}
			}
		}else{
			if(odds.ceiling(d) != null){
				System.out.println(1);
				return;
			}
			
			for(final long s : odds){
				final long diff = Math.abs(d - s);
				
				if(odds.ceiling(diff) != null){
					System.out.println(2);
					return;
				}
			}
		}
		
		System.out.println(-1);
	}
}