from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline

N = int(input())
D = list(map(int,input().split()))
x,y = map(int,input().split())
SD = set(D)
if abs(x)+abs(y) in SD:
    print(1)
    exit()

t = abs(x)+abs(y)

D.sort()

for d in D:
    
    diff = abs(d - t)
    if diff in SD:
        print(2)
        exit()
print(-1)