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

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("Yes")
#define p_no() p("No")

const ll mod = 1e9 + 7;
const ll inf = 1e18;

ll dice(){
    return rand() % 6 + 1;
}

ll dice2(){
    return rand() % 3 + 4;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    double N, K;
    cin >> N >> K;

    ll game = 5000000;
    ll win = 0;
    FOR(i, 0, game){
        // taro
        ll taro = 0;
        FOR(j, 0, N-K){
            taro += dice();
        }
        FOR(j, 0, K){
            taro += dice2();
        }

        // jiro
        ll jiro = 0;
        FOR(j, 0, N){
            jiro += dice();
        }

        if(taro > jiro){
            win++;
        }
    }

    double prob = (double)win / game;
    cout << setprecision(20);
    p(prob);
    
    return 0;
}