#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 a1[6] = {1, 2, 3, 4, 5, 6};
int a2[6] = {4, 4, 5, 5, 6, 6};

vector<double> foo(vector<double>& dp, int a[6]) {
	vector<double> _dp(61);
	for (int i = 0; i <= 60; i++)
		for (int j = 0; j < 6; j++)
			if (i + a[j] <= 60)
				_dp[i + a[j]] += dp[i] / 6;
	return _dp;
}

int main() {
	int N, K; cin >> N >> K;
	vector<double> dp1(61), dp2(61);
	dp1[0] = dp2[0] = 1;
	for (int i = 0; i < N; i++) {
		dp1 = foo(dp1, a1);
		dp2 = foo(dp2, i < K ? a2 : a1);
	}
	double ans = 0;
	for (int i1 = 0; i1 <= 60; i1++)
		for (int i2 = i1 + 1; i2 <= 60; i2++)
			ans += dp1[i1] * dp2[i2];
	cout << ans << endl;
}