from collections import defaultdict, deque
N = int(input())
start, end = map(int,input().split())
s = [start]+list(map(int, input().split()))+[end]

d = {s[i]:i for i in range(N+2)}
G = [list() for _ in range(N+2)]
q = deque
for i in range(N+2):
    for j in range(30):
        G[i].append(s[i]^(1<<j))

q = deque()
dis = [-1]*(N+2)
q.append(0)
dis[0] = 0
while q:
    v = q.popleft()
    for nex in G[v]:
        if nex in d:
            nex_id = d[nex]
            if dis[nex_id]==-1:
                dis[nex_id] = dis[v]+1
                q.append(nex_id)
print(-1 if dis[-1]==-1 else dis[-1]-1)