from collections import deque
#ハミング距離
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]

#BFS
dist=[False]*(n+2)
que=deque([0])
dist[0]=0
while que:
    v=que.popleft()
    for u in range(n+2):
        if hamming(x[v],x[u])==1 and dist[u]==False:
            dist[u]=dist[v]+1
            que.append(u)

res=dist[-1]
if not res:
    print(-1)
else:
    print(res-1)