N, K = $<.map &:to_i
M = 5e5

def valid_dice(n)
  n.times.map{rand(1..6)}.sum
end

def evil_dice(n)
  n.times.map{3+rand(1..3)}.sum
end

p (1..M).count{
  valid_dice(N - K) + evil_dice(K) > valid_dice(N)
} / M