lib LibC
  fun getchar_unlocked : Char
  fun putchar_unlocked(Char)
end

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

def putui(x : Int32)
  if x == 0
    LibC.putchar_unlocked(48)
  else
    ptr = Pointer(UInt8).malloc(5)
    now = ptr + 5
    while x != 0
      now -= 1
      now.value = (48 &+ x % 10).to_u8!
      x //= 10
    end
    STDOUT.write_utf8 Slice.new(now, ptr + 5 - now)
  end
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]
  if i == n &+ 1
    putui(d &- 2)
    LibC.putchar_unlocked(10)
    exit
  end
  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

LibC.putchar_unlocked 45
LibC.putchar_unlocked 49
LibC.putchar_unlocked 10