N = int(input())
s,e = map(int,input().split())
l = list(map(int,input().split()))
l.insert(0,s)
l.append(e)
C = 10 ** 5
dist = [C] * (N + 1)
dist[0] = 0

def hamu(a,b):
    count = 0
    while a != 0 or b != 0:
        if a & 1 != b & 1:
            count += 1
        a >>= 1
        b >>= 1
    return count < 2
    
from collections import deque
q = deque()
q.append(0)
while len(q):
    now = q.popleft()
    for i in range(N+2):
        if memo[i] == C:
            if hamu(l[i],l[now]):
                memo[i] = memo[now] + 1
                q.append(i)
if memo[-1] == C:
    print(-1)
else:
    print(memo[-1])