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())
l = abs(x) + abs(y)
def solve():
    if l == 0: return 0
    elif l in d: return 1
    elif l % 2 == 0: -1 if max(d) * 2 >= l else 2
    else:
        d1 = [x for x in d if x % 2 == 0]
        d2 = [x for x in d if x % 2 == 1]
        if d1 != []:
            for a in d2:
                low = 0
                high = len(d1) - 1
                while low < high:
                    mid = (high + low) >> 1
                    if (a + d1[mid] >= l):
                        high = mid
                    else:
                        low = mid + 1
                if (a + d1[low] < l): continue
                b = low
                low = 0
                high = len(d1) - 1
                while low < high:
                    mid = (high + low + 1) >> 1
                    if (a > d1[mid] or abs(a - d1[mid]) <= l):
                        low = mid
                    else:
                        high = mid - 1
                if (abs(a - d1[low]) > l): continue
                c = low
                if (b <= c): return 2
    return -1
print(solve())