#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cmath>
#include <cstring>
#include <ctime>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; double w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int N, K; cin >> N >> K;
	vector<double> dp1(61);
	dp1[0] = 1;
	for (int i = 0; i < N; i++) {
		vector<double> _dp1(61);
		for (int j = 0; j <= 60; j++)
			if (dp1[j] > 0)
				for (int k = 1; k <= 6; k++)
					_dp1[j + k] += dp1[j] / 6;
		dp1 = _dp1;
	}
	vector<double> dp2(61);
	dp2[0] = 1;
	for (int i = 0; i < N - K; i++) {
		vector<double> _dp2(61);
		for (int j = 0; j <= 60; j++)
			if (dp2[j] > 0)
				for (int k = 1; k <= 6; k++)
					_dp2[j + k] += dp2[j] / 6;
		dp2 = _dp2;
	}
	for (int i = 0; i < K; i++) {
		vector<double> _dp2(61);
		for (int j = 0; j <= 60; j++)
			if (dp2[j] > 0)
				for (int k = 4; k <= 6; k++)
					_dp2[j + k] += dp2[j] / 3;
		dp2 = _dp2;
	}
	double ans = 0;
	for (int j = 0; j <= 60; j++)
		for (int _j = j + 1; _j <= 60; _j++)
			ans += dp1[j] * dp2[_j];
	cout << ans << endl;
}