func main()
	var n: int :: cui@inputInt()
	var k: int :: cui@inputInt()
	
	; dp[i][j][sum]: 回数
	; i: サイコロの個数
	; j: イカサマサイコロの個数
	; sum: サイコロの出目の合計
	var dp: [][][]int :: #[n + 1, k + 1, n * 6 + 1]int
	do dp[0][0][0] :: 1
	for i(0, n - 1)
		for j(0, i)
			for sum(0, i * 6)
				if(j <= k & dp[i][j][sum] <> 0)
					for x(0, 5)
						do dp[i + 1][j][sum + x + 1] :+ dp[i][j][sum]
						if(i < k)
							do dp[i + 1][j + 1][sum + x / 2 + 4] :+ dp[i][j][sum]
						end if
					end for
				end if
			end for
		end for
	end for
	
	var cum: []int :: #[n * 6 + 2]int
	do cum[0] :: 0
	for sum(0, n * 6)
		do cum[sum + 1] :: cum[sum] + dp[n][0][sum]
	end for
	
	var win: int :: 0
	for sum(0, n * 6)
		do win :+ dp[n][k][sum] * cum[sum]
	end for
	
	var total: int :: (6 ^ n) ^ 2
	var ans: float :: win $ float / total $ float
	do cui@print("\{ans}\n")
	
	func comb(n: int, k: int): int
		var res: int :: 1
		for i(0, k - 1)
			do res :* (n - i)
		end for
		for i(1, k)
			do res :/ i
		end for
		ret res
	end func
end func