def solve():
    N = int(input())
    K = int(input())

    ma = 6 * N

    nd = (1, 2, 3, 4, 5, 6)
    id = (4, 5, 6, 4, 5, 6)

    jp = [0] * (ma + 1)
    jp[0] = 1

    for i in range(N):
        for j in range(ma, -1, -1):
            jp[j] = sum(jp[j - k] / 6 for k in nd if j - k >= 0)

    tp = [0] * (ma + 1)
    tp[0] = 1

    for i in range(N):
        ud = id if i < K else nd
        for j in range(ma, -1, -1):
            tp[j] = sum(tp[j - k] / 6 for k in ud if j - k >= 0)

    ans = 0.0
    for i in range(N, ma + 1):
        t = tp[i]
        for j in range(N, i):
            ans += t * jp[j]

    print(ans)


if __name__ == '__main__':
    solve()