n = read_line.to_i
s, t = read_line.split.map(&.to_i)
a = Pointer(Int32).malloc(n + 2)
a.copy_from(read_line.split.map(&.to_i).to_unsafe, n)
a[n] = s
a[n + 1] = t

hash = Hash(Int32, Int32).new(n + 2)
n.times do |i|
  hash[a[i]] = i
end
hash[s] = n
hash[t] = n &+ 1

que = Deque{n}
dist = Pointer(Int32).malloc(n + 2)
dist[n] = 1
while i = que.shift?
  d = dist[i]
  ai = a[i]
  puts(d &- 2) + exit if i == n &+ 1
  bit = 1
  30.times do 
    if (j = hash[ai ^ bit]?) && dist[j] == 0
      dist[j] = d &+ 1
      que << j
    end
    bit <<= 1
  end
end
puts -1