#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <iomanip>
using namespace std;
#define INF 1e9
#define PI acos(-1)
typedef long long ll;

double ziro[15][100] = {0.0};
double taro[15][100] = {0.0};

int main() {
	int n, k;
	cin >> n >> k;

	ziro[0][0] = taro[0][0] = 1;

	for (int i = 0; i < n; i++) {
		for (int j = 0; j < 60; j++) {
			for (int k = 1; k <= 6; k++) {
				ziro[i + 1][j + k] += ziro[i][j]/6;
			}
		}
	}

	for (int i = 0; i < k; i++) {
		for (int j = 0; j < 60; j++) {
			for (int k = 4; k <= 6; k++) {
				taro[i + 1][j + k] += taro[i][j]/3;
			}
		}
	}
	for (int i = k; i < n; i++) {
		for (int j = 0; j < 60; j++) {
			for (int k = 1; k <= 6; k++) {
				taro[i + 1][j + k] += taro[i][j]/6;
			}
		}
	}

	double p = 0.0;
	for (int i = 0; i <= 60; i++) {//二郎の合計を固定
		for (int j = i + 1; j <= 60; j++) {
			p += ziro[n][i] * taro[n][j];
		}
	}
	
	printf("%.8f\n", p);

	return 0;
}