lib LibC
  fun getchar_unlocked : Char
end

def read
  x = 0
  loop do
    c = LibC.getchar_unlocked
    break unless 48 <= c <= 57
    x = x &* 10 &+ (c - 48)
  end
  x
end

n = read
s = read
t = read
a = Pointer(Int32).malloc(n &+ 2)
n.times do |i|
  a[i] = read
end
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 = Pointer(Int32).malloc(n + 2)
que[0] = n
size = 1

dist = Pointer(Int32).malloc(n + 2)
dist[n] = 1
while size != 0
  i = que.value
  que += 1
  size &-= 1
  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[size] = j
      size &+= 1
    end
    bit <<= 1
  end
end
puts -1