import queue
def get_hd(a,b):
    return bin(a^b).count('1')

def solve_slower(start, end, stones):
    checked_set = set()
    que = queue.Queue()
    que.put((start, 0))
    while not que.empty():
        current, distance = que.get()
        next_distance = distance + 1
        if get_hd(current, end) == 1:
            return next_distance - 1
        for candidate in stones:
            if candidate in checked_set:
                continue
            if get_hd(current, candidate) == 1:
                checked_set.add(candidate)
                que.put((candidate, next_distance))
    return -1

if __name__ == '__main__':
    N = int(input())
    start, end = list(map(int, input().split()))
    stones = list(map(int, input().split()))
    print(solve(start, end, stones))