import math
from collections import deque
def is_ham1(a,b):
    if math.log2(a^b).is_integer():
        return True
    else:
        return False

n = int(input())
s,g = map(int,input().split())
ishi = [g]+ list(map(int,input().split()))
q=deque()

q.append([s,0])
S=set()
S.add(s)
while q:
    a = q.popleft()
    S.add(a[0]) 
    for b in ishi:
        if a[0]==b: continue
        if not is_ham1(a[0],b): continue
        if b in S: continue
        if b==g:
            print(a[1])
            exit()
        q.append([b,a[1]+1])

print(-1)