from collections import deque
def BFS(s,N):
    dist=[False]*N
    que=deque([0])
    dist[0]=0
    while que:
        v=que.popleft()
        for u in graph[v]:
            if not dist[u]:
                dist[u]=dist[v]+1
                que.append(u)
    return dist[-1]

def hamming(a,b):
    x=bin(a^b)
    d=0
    for i in x[2:]:
        d+=int(i)
    return d

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

x=[start]+stone+[end]
graph=[[] for i in range(n+2)]
for i in range(n+1):
    for j in range(i+1,n+2):
        if hamming(x[i],x[j])==1:
            graph[i].append(j)
            graph[j].append(i)
            
res=BFS(0,n+2)
if not res:
    print(-1)
else:
    print(res-1)