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