n = read_line.to_i
s, t = read_line.split.map(&.to_i)
a = read_line.split.map(&.to_i)
stones = a + [s, t]
hash = stones.zip(0..).to_h
que = Deque{hash[s]}
dist = [nil.as(Int32?)] * (n + 2)
dist[hash[s]] = -1
while i = que.shift?
  d = dist[i].not_nil!
  puts(d) + exit if i == hash[t]
  (0..30).each do |bit|
    if (j = hash[stones[i] ^ (1 << bit)]?) && dist[j].nil?
      dist[j] = d + 1
      que << j
    end
  end
end
puts -1