from collections import deque
N=int(input())
start,end=map(int,input().split())
S=list(map(int,input().split()))
S.append(end)
S.append(start)

DP=[1<<30]*(N+2)
DP[-1]=0
Q=deque([N+1])

while Q:
    x=Q.popleft()

    for to in range(N+1):
        if (S[x]^S[to]).bit_count()<=1:
            if DP[to]>DP[x]+1:
                DP[to]=DP[x]+1
                Q.append(to)

if DP[-2]>10**5:
    print(-1)
else:
    print(DP[-2]-1)