import sys
from itertools import combinations
readline = sys.stdin.readline
n = int(readline())
d = sorted(map(int, readline().split()))
x, y = map(int, readline().split())
max_xy = abs(x) + abs(y)
def solve():
    if max_xy in d:
        return 1
    for i in d:
        if max_xy + i in d or max_xy - i in d:
            return 2
    return -1
print(solve())