#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<vector>
#include<cmath>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<numeric>
#include<functional>
#include<complex>

using namespace std;
#define BET(a,b,c) ((a)<=(b)&&(b)<(c))
#define FOR(i,n) for(int i=0,i##_end=(int(n));i<i##_end;i++)
#define SZ(x) (int)(x.size())
#define ALL(x) (x).begin(),(x).end()
#define MP make_pair
#define FOR_EACH(it,v) for(__typeof(v.begin()) it=v.begin(),it_end=v.end() ; it != it_end ; it++)
typedef vector<int> VI;
typedef vector<VI> VVI;

int main()
{
    int N,K;
    cin>>N>>K;
    vector<double> dp1(6*N+1);
    vector<double> dp2(6*N+1);
    dp1[0] = 1.0;
    FOR(i,N){
        vector<double> next(6*N+1);
        FOR(j,SZ(dp1)){
            if(dp1[j]){
                for(int k=1;k<=6;k++)
                    next[j+k] += dp1[j] / 6.0;
            }
        }
        dp1.swap(next);
    }
    dp2[0] = 1.0;
    FOR(i,N){
        vector<double> next(6*N+1);
        FOR(j,SZ(dp2)){
            if(dp2[j]){
                if(i < K){
                    for(int k=4;k<=6;k++)
                        next[j+k] += dp2[j] / 3.0;
                }else {
                    for(int k=1;k<=6;k++)
                        next[j+k] += dp2[j] / 6.0;
                }
            }
        }
        dp2.swap(next);
    }
    double ans = 0 ;
    FOR(i,SZ(dp1)) FOR(j,SZ(dp2)){
        if(i < j) ans += dp1[i] * dp2[j];
    }
    printf("%.10f\n", ans);
    return 0;
}