n = gets.to_i
k = gets.to_i
c = 0
1000000.times{|i|
    t = j = 0
    (n - k).times{
        t += rand(1..6)
        j += rand(1..6)
        }
    k.times{
        t += rand(4..6)
        j += rand(1..6)
        }
    if t > j
        c += 1
    end
    }
p c * 1.0 / 1000000