import random
N = int(input())

K = int(input())

ans = 0

for i in range(10 ** 6):
    if sum([random.randrange(6) for j in range(N)]) < sum([random.randrange(6) for j in range(N - K)] + [random.randrange(3, 6) for j in range(K)]):
        ans += 1
        
print(ans / 10 ** 6)