#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <cstdio>
#include <ctime>
#include <assert.h>
#include <chrono>
#include <random>
#include <numeric>
#include <set>
using namespace std;
typedef long long int ll;
typedef unsigned long long ull;

int a[6]={1,2,3,4,5,6};
int b[6]={4,4,5,5,6,6};

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n,k; cin >> n >> k;
    int cnt=0;
    for(int i=0;i<1e6;i++){
        int score=0;
        for(int i=0;i<n;i++){
            score+=a[myRand(6)];
        }
        int score2=0;
        for(int i=0;i<n;i++){
            if(i<k)score2+=b[myRand(6)];
            else score2+=a[myRand(6)];
        }
        if(score2>score)cnt++;
    }
    printf("%.9f\n",(double)(cnt/1e6) );
}