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

jiro = [0 for i in range(70+1)]
taro = [0 for i in range(70+1)]
taro[0] = jiro[0] = 1.0

for k in range(K):
    for i in range(60,-1,-1):
        for j in range(4,7):
            taro[i+j] += taro[i]/3
        taro[i] = 0.0

for k in range(K,N):
    for i in range(60,-1,-1):
        for j in range(1,7):
            taro[i+j] += taro[i]/6
        taro[i] = 0.0

for k in range(N):
    for i in range(60,-1,-1):
        for j in range(1,7):
            jiro[i+j] += jiro[i]/6
        jiro[i] = 0.0

res = 0
for i in range(60+1):
    for j in range(i+1,60+1):
        res += jiro[i] * taro[j]
print(res)