def solve():
    n = int(input())
    dl = dict(zip([int(i) for i in input().split()], [0]*n))
    x, y = map(int, input().split())
    goal = abs(x) + abs(y)
    
    if goal == 0:
        print(0)
        return

    if goal in dl:
        print(1)
        return

    for d in dl.keys():
        tg = abs(goal - d)
        if tg in dl:
            print(2)
            return
    print(-1)

if __name__=='__main__':
    solve()