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

taro_probability = [[0]*61 for _ in range(N+1)]
taro_probability[0][0] = 1
for i in range(N):
    for s in range(55):
        if i < K:
            for j in range(4,7):
                taro_probability[i+1][s+j] += taro_probability[i][s]/3
        else:
            for j in range(1,7):
                taro_probability[i+1][s+j] += taro_probability[i][s]/6
jiro_probability = [[0]*61 for _ in range(N+1)]
jiro_probability[0][0] = 1
for i in range(N):
    for s in range(55):
        for j in range(1,7):
            jiro_probability[i+1][s+j] += jiro_probability[i][s]/6

ans = 0
for t in range(61):
    for j in range(t):
        ans += taro_probability[N][t] * jiro_probability[N][j]
print(ans)