import sys

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

d_even_max = max(d_even) if len(d_even) >= 1 else -1
d_even_min = min(d_even) if len(d_even) >= 1 else -1
d_odd_max = max(d_odd) if len(d_odd) >= 1 else -1
d_odd_min = min(d_odd) if len(d_odd) >= 1 else -1

for d in d_even:
    if (x + y) % 2 == 0:
        if x + y + d >= d_even_min and abs(x + y - d) <= d_even_max:
            print(2)
            sys.exit()
    else:
        if x + y + d >= d_odd_min and abs(x + y - d) <= d_odd_max:
            print(2)
            sys.exit()
for d in d_odd:
    if (x + y) % 2 == 0:
        if x + y + d >= d_odd_min and abs(x + y - d) <= d_odd_max:
            print(2)
            sys.exit()
    else:
        if x + y + d >= d_even_min and abs(x + y - d) <= d_even_max:
            print(2)
            sys.exit()
print(-1)