from itertools import accumulate
from collections import defaultdict

N = int(input())
K = int(input())
U = 6 * N + 1
p1 = 1 / 3
p2 = 1 / 6
val1 = [4, 5, 6]
prob1 = [p1] * 3
val2 = [1, 2, 3, 4, 5, 6]
prob2 = [p2] * 6

# taro
taro = [0] * U
taro[0] = 1
for _ in range(K):
    newDP = [0] * U
    for v, p in zip(val1, prob1):
        for i in range(v, U):
            newDP[i] += taro[i - v] * p
    taro = newDP
for _ in range(N - K):
    newDP = [0] * U
    for v, p in zip(val2, prob2):
        for i in range(v, U):
            newDP[i] += taro[i - v] * p
    taro = newDP

# jiro
jiro = [0] * U
jiro[0] = 1
for _ in range(N):
    newDP = [0] * U
    for v, p in zip(val2, prob2):
        for i in range(v, U):
            newDP[i] += jiro[i - v] * p
    jiro = newDP

jiro.reverse()
jiro_acc = list(accumulate(jiro))
jiro_acc.reverse()

ans = sum(t*(1-j) for t, j in zip(taro, jiro_acc))

print(ans)