N = int(input())
K = int(input())

import time
start = time.time()

edited = [4,5,6]
normal = [1,2,3,4,5,6]

import random
def play(X):
  point = 0
  L = len(X) - 1
  for i in range(K):
    point += X[random.randint(0, L)]
  for i in range(K, N):
    point += normal[random.randint(0, 5)]
  return point
  
win = 0
played = 0
while time.time() - start < 4.9:
  played += 1
  if play(edited) > play(normal):
    win += 1
    
print(win / played)