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()

if len(d_even) >= 2:
    d_even_max = max(d_even)
    d_even.remove(d_even_max)
    d_even_second_max = max(d_even)
    if x + y - d_even_max < d_even_second_max:
        print(2)
        sys.exit()
if len(d_odd) >= 2:
    d_odd_max = max(d_odd)
    d_odd.remove(d_odd_max)
    d_odd_second_max = max(d_odd)
    if x + y - d_odd_max < d_odd_second_max:
        print(2)
        sys.exit()    

print(-1)