class Yukicoder
  def initialize
    n = gets.to_i
    k = gets.to_i

    dp_tarou = Array.new(n+1){ Array.new(n*6+2, 0.0)}
    dp_jirou = Array.new(n+1){ Array.new(n*6+2, 0.0)}

    dp_tarou[0][0] = 1.0
    dp_jirou[0][0] = 1.0

    1.upto(n) do |i|
      0.upto(6*i) do |j|
        if dp_tarou[i-1][j] > 0.0
          1.upto(6) do |k|
            dp_tarou[i][j+k] += 1/6r * dp_tarou[i-1][j]
          end
        end
      end
    end

    1.upto(n-k) do |i|
      0.upto(6*i) do |j|
        if dp_jirou[i-1][j] > 0.0
          1.upto(6) do |k|
            dp_jirou[i][j+k] += 1/6r * dp_jirou[i-1][j]
          end
        end
      end
    end

    (n-k+1).upto(n) do |i|
      0.upto(6*i) do |j|
        if dp_jirou[i-1][j] > 0.0
          4.upto(6) do |k|
            dp_jirou[i][j+k] += 1/3r * dp_jirou[i-1][j]
          end
        end
      end
    end

    answer = 0.0

    0.upto(6*n) do |i|
      (i+1).upto(6*n+1) do |j|
        answer += dp_tarou[n][i] * dp_jirou[n][j]
      end
    end

    puts answer
  end
end

Yukicoder.new