class Yukicoder
  def initialize
    k = gets.chomp.to_i

    dp = Array.new(k+7, 0.0)

    (k-1).downto(0) do |x|
      dp[x] = (x+1..x+6).inject(0){|sum, e| sum += 1/6r * dp[e]} + 1.0
    end

    puts dp[0]
  end
end

Yukicoder.new