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) for i in range(N + 1)]
    jp[0][0] = 1

    for i in range(N):
        for j in range(ma - 5):
            for k in nd:
                jp[i + 1][j + k] += jp[i][j] / 6

    tp = [[0] * (ma + 1) for i in range(N + 1)]
    tp[0][0] = 1

    for i in range(N):
        ud = id if i < K else nd
        for j in range(ma - 5):
            for k in ud:
                tp[i + 1][j + k] += tp[i][j] / 6

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

    print(ans)


if __name__ == '__main__':
    solve()