#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <functional>
#include <set>
#include <numeric>
#include <stack>
#include <utility>
#include <time.h>
//#include "util.h"

using namespace std;
typedef long long ll;
typedef unsigned long long ull;

#define PI 3.14159265358979323846
#define EPS 1e-6
#define MOD ((ll)1000000007)
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))
#define CHAR_BIT 8

template <typename _Ty>
ostream& operator << (ostream& ostr, const vector<_Ty>& v) {
	if (v.empty()) {
		cout << "{ }";
		return ostr;
	}
	cout << "{" << v.front();
	for (auto itr = ++v.begin(); itr != v.end(); itr++) {
		cout << ", " << *itr;
	}
	cout << "}";
	return ostr;
}

int yuki0058()
{
	int N, K;
	cin >> N >> K;

	// fair[i][j] : 公正なサイコロを i 個振って出目の和が j となる確率
	double fair[11][61] = { 0 };
	// cheat[i][j] : イカサマサイコロを i 個振って出目の和が j となる確率
	double cheat[11][61] = { 0 };

	fair[0][0] = cheat[0][0] = 1.0;

	for (int j = 1; j <= 6; j++) fair[1][j] = (double)1 / 6;
	for (int j = 4; j <= 6; j++) cheat[1][j] = (double)1 / 3;

	for (int i = 2; i <= 10; i++) {
		for (int j = 0; j <= 60; j++) {
			for (int k = 0; k <= j; k++) {
				fair[i][j] += fair[i - 1][k] * fair[1][j - k];
				cheat[i][j] += cheat[i - 1][k] * cheat[1][j - k];
			}
		}
	}

	double Taro[61] = { 0 };
	double Jiro[61] = { 0 };

	for (int k = 0; k <= 60; k++) {
		for (int i = 0; i <= k; i++)
			Taro[k] += fair[N - K][i] * cheat[K][k - i];
		Jiro[k] = fair[N][k];
	}

	double ans = 0, sumJ;

	// Taro が勝つ : Taro の出目が k で Jiro の出目が k 未満となる
	for (int k = 1; k <= 60; k++) {
		sumJ = 0;
		for (int i = 1; i < k; i++)
			sumJ += Jiro[i];
		ans += Taro[k] * sumJ;
	}

	cout << ans << endl;

	return 0;
}

int main()
{
	//clock_t start, end;
	//start = clock();

	yuki0058();

	//end = clock();
	//printf("%d msec.\n", end - start);

	return 0;
}