import sys
readline = sys.stdin.readline

n = int(input())
d_arr = list(map(int, readline().split()))
d_even = []
d_odd = []
for d in d_arr:
    if d % 2 == 0:
        d_even.append(d)
    else:
        d_odd.append(d)
d_even.sort()
d_odd.sort()
x, y = map(lambda n: abs(int(n)), input().split())

if x == 0 and y == 0:
    print(0)
    sys.exit()

for d in d_arr:
    if d == x + y:
        print(1)
        sys.exit()


def find(x, i):
    if len(x) == 0:
        return -1

    low = 0
    high = len(x) - 1
    t = (low + high) // 2

    while low <= high:
        if (i == x[t]):
            break
        elif (i > x[t]):
            low = t + 1
        elif (i < x[t]):
            high = t - 1
        t = (low + high) // 2

    if (i == x[t]):
        print(2)
        sys.exit()
    else:
        return t + 1


for d in d_even:
    if (x + y) % 2 == 0:
        if find(d_even, abs(x + y - d)) < find(d_even, x + y + d):
            print(2)
            sys.exit()
    else:
        if find(d_odd, abs(x + y - d)) < find(d_odd, x + y + d):
            print(2)
            sys.exit()
for d in d_odd:
    if (x + y) % 2 == 0:
        if find(d_odd, abs(x + y - d)) < find(d_odd, x + y + d):
            print(2)
            sys.exit()
    else:
        if find(d_even, abs(x + y - d)) < find(d_even, x + y + d):
            print(2)
            sys.exit()
print(-1)