from collections import defaultdict, deque
from itertools import combinations


def main():
    _ = int(input())
    st, gl = map(int, input().split())
    a = [st] + list(map(int, input().split())) + [gl]

    edge = defaultdict(list)
    for u, v in combinations(a, 2):
        if bin(u ^ v).count('1') == 1:
            edge[u].append(v)
            edge[v].append(u)

    q = deque()
    q.append(st)
    dist = defaultdict(lambda: -1)
    dist[st] = 0
    while q:
        v = q.popleft()
        for i in edge[v]:
            if i == gl:
                exit(print(dist[v]))
            if dist[i] == -1:
                dist[i] = dist[v] + 1
                q.append(i)
    print(-1)


if __name__ == "__main__":
    main()