from collections import deque

def hamming_distance(a: int, b: int) -> int:
    x = a ^ b
    return bin(x)[2:].count("1")

n = int(input())
start, end = map(int, input().split(" "))
stones = list(map(int, input().split(" ")))

que = deque([])
que.append((0, start))

while len(que):
    cnt, now = que.popleft()

    if hamming_distance(now, end) == 1:
        print(cnt)
        break

    for stone in stones:
        if hamming_distance(now, stone) == 1:
            que.append((cnt+1, stone))
            stones.remove(stone)
else:
    print(-1)