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

while Q:
    x=Q.popleft()
    for y in range(N+2):
        if Hamming(V[x],V[y])==1 and X[y]==-1:
            X[y]=X[x]+1
            Q.append(y)

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