N = int(input())
s,e = map(int,input().split())
S = [s] + list(map(int,input().split())) + [e]
N += 2

def check(X, Y):
    L = len(bin(max(X,Y))[2:])
    X = bin(X)[2:].zfill(L)
    Y = bin(Y)[2:].zfill(L)
    cnt = 0
    for i in range(L):
        if X[i] != Y[i]:
            cnt += 1
            if cnt > 1:
                return False
    return True

G = [[] for i in range(N)]
for i in range(N - 1):
    for j in range(i + 1, N):
        if check(S[i], S[j]):
            G[i].append(j)
            G[j].append(i)
            
from collections import deque
q = deque([])
q.append([0, 0])
visited = [False] * N
visited[0] = True
while q:
    v, c = q.popleft()
    if v == N - 1:
        print(c - 1)
        break
    for child in G[v]:
        if visited[child]:
            continue
        visited[child] = True
        q.append([child, c + 1])
else:
    print(-1)