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

    goal = abs(X) + abs(Y)
    if goal == 0:
        print(2)
    elif goal in D:
        print(1)
    else:
        for i in D:
            if abs(goal - i) in D:
                print(2)
                break
        else:
            print(-1)

main()