n = int(input())
m = int(input())

DP1 = [[0.0 for _ in range(6 * n + 1)] for _ in range(n + 1)]
DP2 = [[0.0 for _ in range(6 * n + 1)] for _ in range(n + 1)]
DP1[0][0] = 1.0
DP2[0][0] = 1.0
for i in range(n):
    for j in range(6 * n + 1):
        if DP1[i][j] > 0.0:
            if i < m:
                for k in (4, 5, 6):
                    DP1[i + 1][j + k] += DP1[i][j] / 3
            else:
                for k in range(1, 7):
                    DP1[i + 1][j + k] += DP1[i][j] / 6
        if DP2[i][j] > 0.0:
            for k in range(1, 7):
                DP2[i + 1][j + k] += DP2[i][j] / 6
ans = 0.0
for i in range(6 * n + 1):
    if DP2[n][i] > 0.0:
        p = DP2[n][i]
        res = 0.0
        for j in range(i + 1, 6 * n + 1):
            res += DP1[n][j]
        ans += res * p
print(ans)