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

jiro = [[0] * (6*N + 1) for _ in range(N + 1)]
jiro[0][0] = 1

for i in range(N):
    for j in range(6*N + 1):
        if jiro[i][j] == 0:
            continue
        for k in range(1, 7):
            # j + k
            jiro[i + 1][j + k] += jiro[i][j]/6

taro = [[0] * (6*N + 1) for _ in range(N + 1)]
taro[0][0] = 1

for i in range(N):
    for j in range(6*N + 1):
        if taro[i][j] == 0:
            continue
        if i < K:
            for k in range(4, 7):
                # j + k
                taro[i + 1][j + k] += taro[i][j]/3
        else:
            for k in range(1, 7):
                taro[i + 1][j + k] += taro[i][j]/6

ans = 0
for j in range(6*N + 1):
    for t in range(j + 1, 6*N + 1):
        ans += jiro[-1][j] * taro[-1][t]
print(ans)