import sys

sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()
dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = 18446744073709551615
inf = 4294967295
md = 10**9+7
# md = 998244353

from bisect import *

def solve():
    n = II()
    dd = LI()
    dd.sort()
    x, y = LI()
    x, y = abs(x+y), abs(x-y)
    if x < y: x, y = y, x

    if x == 0:
        print(0)
        return

    if x in dd:
        print(1)
        return

    dd0, dd1 = [], []
    for d in dd:
        if d & 1: dd1.append(d)
        else: dd0.append(d)

    mx0 = mx1 = -1
    if dd0: mx0 = max(dd0)
    if dd1: mx1 = max(dd1)

    if x%2 == 0:
        if x <= mx1*2 or x <= mx0*2:
            print(2)
        else:
            print(-1)
        return

    if dd0 and dd1:
        for d0 in dd0:
            i = bisect_left(dd1, abs(x-d0))
            if i < len(dd1) and dd1[i] <= x+d0:
                print(2)
                return

    print(-1)

solve()