# test7.rb

require 'list'

def test7 ()
  my_list = [14, 198, 47, 918, 405, 578, 46]
  target = 405
  position = 0
  while ! (my_list == []) && head (my_list) != target
    my_list = tail (my_list)
    position = position + 1
  end
  if my_list == []
    puts -1
  else
    puts position
  end
  return 0
end

test7 ()