def popcount(x):
    return bin(x).count("1")

def Hamming(x,y):
    return popcount(x^y)
#==================================================
from collections import deque

N=int(input())
S,G=map(int,input().split())
A=list(map(int,input().split()))

V=[S,G]+A
V_set=set(V)
V_ind={v:i for i,v in enumerate(V)}

E=[[] for _ in range(N+2)]
for i in range(N+2):
    w=1
    for _ in range(40):
        if V[i]^w in V_set:
            E[i].append(V_ind[V[i]^w])
        w<<=1

X=[-1]*(N+2); X[0]=0
Q=deque([0])

while Q:
    x=Q.popleft()
    for y in E[x]:
        if X[y]==-1:
            X[y]=X[x]+1
            Q.append(y)

print(X[1]-1 if X[1]!=-1 else -1)