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

C = 6 * N 
dp = [0] * (C + 1)
dp[0] = 1
dp2 = [0] * (C + 1)
dp2[0] = 1
for _ in range(N):
    nx = [0] * (C + 1)
    for i in range(C+1):
        if dp[i]:
            for j in range(1,7):
                nx[i+j] += dp[i] / 6
    dp = nx
for _ in range(K):
    nx = [0] * (C + 1)
    for i in range(C + 1):
        if dp2[i]:
            for j in range(4,7):
                nx[i + j] += dp2[i] / 3
    dp2 = nx
for _ in range(N - K):
    nx = [0] * (C + 1)
    for i in range(C+1):
        if dp2[i]:
            for j in range(1,7):
                nx[i+j] += dp2[i] / 6
    dp2 = nx
ans = 0
_sum = 0
for i in range(1,C+1):
    ans += dp2[i] * _sum
    _sum += dp[i]
print(ans)