#include<bits/stdc++.h>
using namespace std;

#define M1 					1000000007
#define M2 					998244353
#define ll 					long long int
#define pll 				pair<ll,ll>
#define mll 				map<ll,ll>
#define F 					first
#define S 					second
#define PB 					push_back
#define mp 					make_pair
#define lb 					lower_bound
#define ub 					upper_bound
#define V(a) 				vector<a>
#define endl 				'\n'
#define test(t) 			while(t--)
#define PI 					acos(-1.0)
#define rep(i,a,b) 			for(ll i=a;i<b;i++)
#define repp(i,b,a) 		for(ll i=b-1;i>=a;i--)
#define clr(ar, val)		memset(ar, val, sizeof(ar))
#define setbits(x) 			__builtin_popcountll(x)
#define zrobits(x) 			__builtin_ctzll(x)
#define ps(y) 				fixed << setprecision(y)
#define all(x) 				begin(x),end(x)
#define allr(x) 			rbegin(x),rend(x)
const int inf= 				0x3f3f3f3f;
const ll INF= 				0x3f3f3f3f3f3f3f3f;
const int dx[4]= 			{ 0, -1, 0, 1 };
const int dy[4]= 			{ -1, 0, 1, 0 };



class EmptyTheBox{
    public:
    double Calculate(long long int subset){
        double t = 1,sum=0;
        while(subset > 0){
            if (subset&1) sum += t;
            subset >>=1;
            t++;
        }
        return sum;
    }

	double minExpectedPenalty(int D, int T){
		
		double* rollprob = new double[2*D+1]();
		for(int i = 1; i<=D;++i){
			for (int j = 1; j<=D;++j){
				rollprob[i+j] += 1./(D*D);
			}
		}
        int excess = 0;
        while(T > 2*D) excess+=T,T--;
        T = min(2*D,T);
        double* dp = new double[1<<T]();
        for(long long int subset = 0; subset<(1<<T);++subset){
            for (int roll = 2; roll <= 2*D; ++roll){
                double X = Calculate(subset);
                for(long long int reduceset = 1;reduceset < (1<<T);++reduceset){
                    if (((subset&reduceset) == reduceset) && (Calculate(reduceset) == roll)){
                            X = min(X,dp[subset^reduceset]);
                    }
                }
                dp[subset] += rollprob[roll]*X;
            } 
        }
        return (dp[(1<<T)-1] + excess);
	}	
};

// int main(){
//     int d,t;
//     cin >> d >> t;
//     EmptyTheBox empbx;
//     cout << empbx.minExpectedPenalty(d,t) << endl;
// }