#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <cstring>

typedef long long ll;
using namespace std;

#define mod 1000003
#define INF 10000000
#define LLINF 2000000000000000000LL

#define SIZE 10000

int n,k;
ll dice[2][70];

void dfs(int p,int h=0,int sum=0){
    
    if(h==n){
        dice[p][sum]++;
        return;
    }
    
    if(h<k && p==0){
        for(int i=4;i<=6;i++){
            dfs(p,h+1,sum+i);
            dfs(p,h+1,sum+i);
        }
    }else{
        for(int i=1;i<=6;i++){
            dfs(p,h+1,sum+i);
        }
    }
    
}

int main(){
    ll M=0,C=0;
    
    
    scanf("%d%d",&n,&k);
    
    dfs(0);
    dfs(1);
    
    for(int i=6*n;i>=1;i--){
        dice[0][i-1]+=dice[0][i];
    }
    
    M=dice[0][0]*dice[0][0];
    
    for(int i=1;i<=60;i++){
        C+=dice[1][i]*dice[0][i+1];
    }
    
    printf("%.5lf",(double)C/M);
    
    return 0;
}