#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
int INF = 1e9;
int MOD = 1000000007;
double dpa[11][61];
double dpb[11][61];
main(){
    dpa[0][0] = 1;
    dpb[0][0] = 1;
    for(int i = 0;i < 10;i++){
        for(int j = 0;j <= 54;j++){
            for(int k = 1;k <= 6;k++){
                dpa[i+1][j+k] += dpa[i][j] / 6;
            }
        }
    }
    int N,K;
    cin >> N >> K;
    for(int i = 0;i < K;i++){
        for(int j = 0;j <= 54;j++){
            for(int k = 4;k <= 6;k++){
                dpb[i+1][j+k] += dpb[i][j] / 3;
            }
        }
    }
    for(int i = K;i < N;i++){
        for(int j = 0;j <= 54;j++){
            for(int k = 1;k <= 6;k++){
                dpb[i+1][j+k] += dpb[i][j] / 6;
            }
        }
    }
    double ans = 0;
    for(int i = 60;i >= 0;i--){
        for(int j = 60;j >= 0;j--){
            if(i <= j)continue;
            ans += dpa[N][j] * dpb[N][i];
        }
    }
    cout << ans << endl;
}