N = int(input())
K = int(input())
X = [1] + [0] * 60
Y = [0,1,1,1,1,1,1]
Z = [0,0,0,0,2,2,2]
M = 6 ** N
for i in range(N-K):
    X2 = [0] * 61
    for j in range(61):
        for k in range(1,7):
            if j + k <= 60:
                X2[j+k] += X[j] * Y[k]
    X,X2 = X2,X

XB = X[:]
for i in range(K):
    X2 = [0] * 61
    for j in range(61):
        for k in range(1,7):
            if j + k <= 60:
                X2[j+k] += X[j] * Y[k]
    X,X2 = X2,X
for i in range(1,61):
    X[i] += X[i-1]

for i in range(K):
    X2 = [0] * 61
    for j in range(61):
        for k in range(1,7):
            if j + k <= 60:
                X2[j+k] += XB[j] * Z[k]
    XB,X2 = X2,XB
tmp = 0
for i in range(1,61):
    tmp += XB[i] * X[i-1]
print(tmp/M/M)