import sys

n = int(input())
d_arr = list(map(int, input().split()))
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()

odd = 0
even = 0
for d in d_arr:
    if d % 2 == 0:
        even += 1
    else:
        odd += 1
    if even >= 2 or odd >= 2:
        print(2)
        sys.exit()

print(-1)