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

#define int long long

typedef pair<int,int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
template<class T,class U>void chmin(T &t,U f){if(t>f)t=f;}
template<class T,class U>void chmax(T &t,U f){if(t<f)t=f;}

int times=10000000;

signed main(){
    srand((unsigned)time(NULL));

    int N,K;cin>>N>>K;

    int win=0;
    rep(_,times){
        int a=0,b=0;
        rep(i,N)b+=rand()%6+1;
        rep(i,K)a+=rand()%3+4;
        rep(i,N-K)a+=rand()%6+1;
        if(a>b)win++;
    }

    printf("%.20lf\n",1.0*win/times);
    return 0;
}