class Sequence
  def initialize(start_num)
    @start_num = start_num
  end

  attr_accessor :start_num

  def num(idx)
    even_num = idx / 2
    odd_num = (idx - 1) / 2
    return @start_num * 2 ** even_num / (3 ** odd_num)
  end
end

while start_num = gets
  sum = 0.0
  seq = Sequence.new(start_num.to_f)
  (1..10).each do |n|
    sum += seq.num(n)
  end
  puts sum.round(7)
end