from collections import Counter
from collections import deque
# import time
# start_time = time.time()

def hmg_d(a, b):
    count = Counter(list(bin(a ^ b)))
    if count["1"] == 1:
        return True
    else:
        return False

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

if hmg_d(start, end):
    print(0)
    exit()

stone_dict = {}
stone_dict[start] = 0
for i in stone:
    stone_dict[i] = 0

queue = deque()
queue.append(start)

while queue:
    v = queue.popleft()
    l = []
    for i in stone:
        if hmg_d(v, i):
            if stone_dict[i] == 0:
                stone_dict[i] = stone_dict[v] + 1
                queue.append(i)
            if hmg_d(i, end):
                print(stone_dict[i])
                # print(time.time() - start_time)
                exit()
            
            l.append(i)
    
    for i in l:
        stone.remove(i)


print(-1)