from bisect import bisect

def main():
    N = int(input())
    D = tuple(map(int, input().split()))
    X, Y = map(int, input().split())

    p = abs(X) + abs(Y)
    if N == 1:
        if p % D[0]:
            print(-1)
        else:
            print(p // D[0])
        return

    n = 1
    while 1:
        if p in D:
            print(n)
            break
        prev = p
        i = bisect(D, p)
        p = min(abs(p - D[i-1]), abs(p - D[i]))
        if p >= prev:
            print(-1)
            break
        prev = p
        n += 1

main()