N = int(input())
K = int(input())
jiro = [[0 for j in range(70 + 1)] for i in range(N + 1)]
taro = [[0 for j in range(70 + 1)] for i in range(N + 1)]
jiro[0][0] = 1.0
taro[0][0] = 1.0
for i in range(N):
	for j in range(60,-1,-1):
		for k in range(1,6 + 1):
			jiro[i + 1][j + k] += jiro[i][j] / 6
for i in range(K):
	for j in range(60,-1,-1):
		for k in range(4,6 + 1):
			if j + k > 60:continue
			taro[i + 1][j + k] += taro[i][j] / 3
for i in range(K,N):
	for j in range(60,-1,-1):
		for k in range(1,6 + 1):
			if j + k > 60:continue
			taro[i + 1][j + k] += taro[i][j] / 6
ans = 0.0
for i in range(60 + 1):
	for j in range(i + 1,60 + 1):
		ans += jiro[N][i] * taro[N][j]
print (ans)