import bisect

def main():
    import sys
    input = sys.stdin.read().split()
    idx = 0
    n = int(input[idx])
    idx += 1
    d_list = list(map(int, input[idx:idx + n]))
    idx += n
    x = int(input[idx])
    y = int(input[idx + 1])
    idx += 2

    if x == 0 and y == 0:
        print(0)
        return

    D = abs(x) + abs(y)
    d_set = set(d_list)
    if D in d_set:
        print(1)
        return

    evens = []
    odds = []
    for d in d_list:
        if d % 2 == 0:
            evens.append(d)
        else:
            odds.append(d)
    evens.sort()
    odds.sort()

    for di in d_list:
        lower = abs(D - di)
        upper = D + di
        required_parity = (D + di) % 2
        if required_parity == 0:
            target_list = evens
        else:
            target_list = odds

        left = bisect.bisect_left(target_list, lower)
        right = bisect.bisect_right(target_list, upper)
        if left < right:
            print(2)
            return

    print(-1)

if __name__ == "__main__":
    main()