#!/usr/local/bin/ruby
class FakeDice
  def initialize(*arg)
    @n,@k = arg
    @jirodice = normal_dice_pb(@n)
    @tarodice = fake_dice_pb(@k,normal_dice_pb(@n-@k))
  end

  private
  def normal_dice_pb(n)
    dp = Hash.new(0)
    dp[0]=1
    n.times do
      newdp = Hash.new(0)
      dp.each do |dsum,pb|
        (1..6).each do |i|
          newdp[dsum+i] += pb/6.to_r
        end
      end
      dp = newdp
    end
    dp
  end
  def fake_dice_pb(k,dp)
    k.times do
      newdp = Hash.new(0)
      dp.each do |dsum,pb|
        (4..6).each do |i|
          newdp[dsum+i] += pb/3.to_r
        end
      end
      dp = newdp
    end
    dp
  end

  public

  def ans
    cumsum = Array.new(@n*6+2,0)
    d = @n*6
    while d >= @n+1
      cumsum[d] = cumsum[d+1] + @tarodice[d]
      d-=1
    end
    r = 0
    d =@n
    while d < @n*6
      r += @jirodice[d]*cumsum[d+1]
      d+=1
    end
    r.to_f
  end
end
### END: class FakeDice
iod = STDIN
n = iod.gets.to_i
k = iod.gets.to_i
puts FakeDice.new(n,k).ans
exit 0