from collections import deque
# import time

def hmg_d(a, b):
    x = bin(a ^ b)
    cnt = 0
    for i in x:
        if i == "1":
            cnt += 1
        if cnt > 1:
            return False
    if cnt == 1:
        return True
    else:
        return False

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

# start_time = time.time()

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

stone_dict = {}
stone_dict[start] = 0
end_dict = {}
for i in stone:
    stone_dict[i] = 0
    end_dict[i] = 0
    if hmg_d(i, end):
        end_dict[i] = 1

queue = deque()
queue.append(start)

while queue:
    v = queue.popleft()
    l = []
    for i in stone:
        if hmg_d(v, i):
            stone_dict[i] = stone_dict[v] + 1
            queue.append(i)

            # 終了条件
            if end_dict[i] == 1:
                print(stone_dict[i])
                # print(time.time() - start_time)
                exit()
            
            l.append(i)
    
    for i in l:
        stone.remove(i)

print(-1)