n = int(input())
k = int(input())

dp1 = [[0 for _ in range(150)] for _ in range(20)]
dp2 = [[0 for _ in range(150)] for _ in range(20)]

dp1[0][0] = 1.0
dp2[0][0] = 1.0

for i in range(1, n + 1):
    for j in range(1, i * 6 + 1):
        if i <= k:
            for x in range(4, 7):
                if j - x >= 0:
                    dp1[i][j] += dp1[i - 1][j - x] / 3.0
        else:
            for x in range(1, 7):
                if j - x >= 0:
                    dp1[i][j] += dp1[i - 1][j - x] / 6.0
                    
for i in range(1, n + 1):
    for j in range(1, i * 6 + 1):
        for x in range(1, 7):
            if j - x >= 0:
                dp2[i][j] += dp2[i - 1][j - x] / 6.0
                
ans = 0
for sum1 in range(1, n * 6 + 1):
    for sum2 in range(sum1):
        ans += dp1[n][sum1] * dp2[n][sum2]
        
print(ans)