#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
using ll=long long;
using ld=long double;
ld pie=3.141592653589793;
ll mod=998244353;
ll inf=1009999999999999990;
int main(){
    ll n,k;
    cin >> n >> k;
    ld ans=0;
    for (ll i = 0; i < 10000000; i++)
    {
        ll x=0;
        for (ll j = 0; j < k; j++)
        {
            x+=rand()%3+4;
        }
        for (ll j = 0; j < n-k; j++)
        {
            x+=rand()%6+1;
        }
        for (ll j = 0; j < n; j++)
        {
            x-=rand()%6+1;
        }
        if (x>0)
        {
            ans++;
        }
    }
    ans/=10000000.0;
    cout << setprecision(100) << ans << endl;
}