import sys
from collections import defaultdict, Counter, deque
from itertools import permutations, combinations, product, combinations_with_replacement, groupby, accumulate
import operator
from math import sqrt, gcd, factorial
# from math import isqrt, prod,comb  # python3.8用(notpypy)
#from bisect import bisect_left,bisect_right
#from functools import lru_cache,reduce
from heapq import heappush, heappop, heapify, heappushpop, heapreplace
#import numpy as np
#import networkx as nx
#from networkx.utils import UnionFind
#from numba import njit, b1, i1, i4, i8, f8
#from scipy.sparse import csr_matrix
#from scipy.sparse.csgraph import shortest_path, floyd_warshall, dijkstra, bellman_ford, johnson, NegativeCycleError
# numba例 @njit(i1(i4[:], i8[:, :]),cache=True) 引数i4配列、i8 2次元配列,戻り値i1
def input(): return sys.stdin.readline().rstrip()
def divceil(n, k): return 1+(n-1)//k  # n/kの切り上げを返す
def yn(hantei, yes='Yes', no='No'): print(yes if hantei else no)


def main():
    n = int(input())
    s, t = map(int, input().split())
    A = list(map(int, input().split()))

    dist = {AA:-1 for AA in A}
    dist[s] = 0
    dist[t] = -1
    d=deque()
    d.append(s)
    while d:
        v = d.popleft()
        for ii in range(30):
            i = v ^ (2**ii)
            if i not in dist:
                continue
            if dist[i] != -1:
                continue
            dist[i] = dist[v] + 1
            d.append(i)

    print(-1 if dist[t]==-1 else dist[t]-1)


if __name__ == '__main__':
    main()