# coding:UTF-8
import sys

input = sys.stdin.buffer.readline

MOD = 10 ** 9 + 7
INF = float('inf')

N = int(input())    # 数字
K = int(input())    # 数字

score_min = N * 1
score_max = N * 6

dp_j = [[0] * (score_max + 1) for _ in range(N + 1)]
dp_j[0][0] = 1
for i in range(1, N+1):
    for j in range(score_max+1):
        for c in range(1, 7):
            if j - c >= 0:
                dp_j[i][j] += dp_j[i-1][j-c] / 6

dp_t = [[0] * (score_max + 1) for _ in range(N + 1)]
dp_t[0][0] = 1
for i in range(1, K+1):
    for j in range(score_max+1):
        for c in range(4, 7):
            if j - c >= 0:
                dp_t[i][j] += dp_t[i-1][j-c] / 3
for i in range(K+1, N+1):
    for j in range(score_max+1):
        for c in range(1, 7):
            if j - c >= 0:
                dp_t[i][j] += dp_t[i-1][j-c] / 6

dp_t_sum = [0] * (score_max + 1)
for i in range(1, score_max + 1):
    dp_t_sum[i] = dp_t_sum[i-1] + dp_t[N][i]

res = 0
for score in range(score_min, score_max+1):
    t = (dp_t_sum[score_max] - dp_t_sum[score]) * dp_j[N][score]
    res += t

print("{}".format(res))