//////////////////////////////
// Check before you submit.
// #define _ATCODER_LIBRARY

const long long MOD = 1e9+7;
// const long long MOD = 998244353;

/////////////////////////////
#include <bits/stdc++.h>
using namespace std;
#include <boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;

#ifdef _ATCODER_LIBRARY
#include <atcoder/all>
using namespace atcoder;
#endif
// _ATCODER_LIBRARY

const long long INF = 1LL << 60;
const double PI = acos(-1);
using ll = long long;
using P = pair<ll, ll>;


#define FOR(i,a,b) for (ll i=(a);i<(ll)(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
#define SUM(v) accumulate(ALL(v),0ll)

template<typename T>istream& operator>>(istream&i,vector<T>&v){REP(j,v.size())i>>v[j];return i;}
template<typename T>string join(vector<T>&v){stringstream s;REP(i,v.size())s<<' '<<v[i];return s.str().substr(1);}
template<typename T>ostream& operator<<(ostream&o,vector<T>&v){if(v.size())o<<join(v);return o;}
template<typename T>string join(vector<vector<T>>&vv){string s="\n";REP(i,vv.size())s+=join(vv[i])+"\n";return s;}
template<typename T>ostream& operator<<(ostream&o,vector<vector<T>>&vv){if(vv.size())o<<join(vv);return o;}
template<typename T1,typename T2>istream& operator>>(istream&i,pair<T1,T2>&v){return i>>v.first>>v.second;}
template<typename T1,typename T2>ostream& operator<<(ostream&o,pair<T1,T2>&v){return o<<v.first<<","<<v.second;}

#define DEBUG(x);

#ifdef _DEBUG
#define DEBUG(x) std::cerr << #x << " : " << (x) << std::endl;
#define GLIBCXX_DEBUG
#define GLIBCXX_DEBUG_PEDANTIC
#endif
// _DEBUG

int dx[4]{0, 1, 0, -1};
int dy[4]{1, 0, -1, 0};

void init_init_init() {ios_base::sync_with_stdio(false);cin.tie(NULL);std::cout<<fixed<<setprecision(10);}
template<class T>T up(T a, T b){assert(b);return (a+b-1)/b;}
template<typename... A>bool eq(A const&... a){auto t={a...};assert(t.size());auto tar=*t.begin();for(const auto&e:t)if(tar!=e)return false;return true;}

template<class T>bool chmin(T &a, T b){if(a>b){a=b;return false;}return true;}
template<class T>bool chmax(T &a, T b){if(a<b){a=b;return false;}return true;}
template<class T>bool chmax(T &a, initializer_list<T>l){return chmax(a,max(l));}
template<class T>bool chmin(T &a, initializer_list<T>l){return chmin(a,min(l));}

//////////////////////////////////////////////////////////////////
// My Library
//////////////////////////////////////////////////////////////////



//////////////////////////////////////////////////////////////////
// Contest Code
//////////////////////////////////////////////////////////////////

vector<ll> normal{1, 2, 3, 4, 5, 6};
vector<ll> ikasama{4, 4, 5, 5, 6, 6};
double dp1[110][1000]{};
double dp2[110][1000]{};

int main(int argc, char **argv)
{
	init_init_init();

	ll N, K; cin >> N >> K;
	dp1[0][0] = dp2[0][0] = 1.f;
	REP(i, N)
	{
		REP(sum, 1000)
		{
			REP(j, 6)
			{
				if (sum-normal[j]>=0)
					dp1[i+1][sum] += dp1[i][sum-normal[j]] / 6;
			}

			REP(j, 6)
			{
				if (i < K)
				{
					if (sum-ikasama[j]>=0)
						dp2[i+1][sum] += dp2[i][sum-ikasama[j]] / 6;
				}
				else
				{
					if (sum-normal[j]>=0)
						dp2[i+1][sum] += dp2[i][sum-normal[j]] / 6;
					
				}
			}
		}
	}

	double res{0.f};
	REP(i, 1000)
		for (ll j = i+1; j<1000; ++j)
			res += dp1[N][i] * dp2[N][j];
	std::cout << res << std::endl;
}