#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<ll, ll> p_ll;

template<class T>
void debug(T itr1, T itr2) { auto now = itr1; while(now<itr2) { cout << *now << " "; now++; } cout << endl; }
#define repr(i,from,to) for (int i=(int)from; i<(int)to; i++)
#define all(vec) vec.begin(), vec.end()
#define rep(i,N) repr(i,0,N)
#define per(i,N) for (int i=(int)N-1; i>=0; i--)

const ll MOD = pow(10,9)+7;
const ll LLINF = pow(2,61)-1;
const int INF = pow(2,30)-1;

vector<ll> fac;
void c_fac(int x=pow(10,6)+10) { fac.resize(x,true); rep(i,x) fac[i] = i ? (fac[i-1]*i)%MOD : 1; }
ll inv(ll a, ll m=MOD) { ll b = m, x = 1, y = 0; while (b!=0) { int d = a/b; a -= b*d; swap(a,b); x -= y*d; swap(x,y); } return (x+m)%m; }
ll nck(ll n, ll k) { return fac[n]*inv(fac[k]*fac[n-k]%MOD)%MOD; }
ll gcd(ll a, ll b) { if (a<b) swap(a,b); return b==0 ? a : gcd(b, a%b); }
ll lcm(ll a, ll b) { return a/gcd(a,b)*b; }


int main() {
  ll N, K; cin >> N >> K;
  double dp1[N+1][6*N+1] = {}, dp2[N+1][6*N+1] = {};
  dp1[0][0] = 1; dp2[0][0] = 1;

  rep(i,N) rep(j,6*i+1) {
    rep(k,6) dp1[i+1][j+k+1] += dp1[i][j]/6;
    if (i<K) rep(k,3) dp2[i+1][j+k+4] += dp2[i][j]/3;
    else rep(k,6) dp2[i+1][j+k+1] += dp2[i][j]/6;
  }
  // debug(dp1[N],dp1[N]+6*N+1); debug(dp2[N],dp2[N]+6*N+1);

  double p1[6*N+1] = {}; rep(i,6*N+1) p1[i] = dp1[N][i];
  double p2[6*N+1] = {}; per(i,6*N+1) p2[i] = i==6*N ? dp2[N][i] : p2[i+1]+dp2[N][i];
  // debug(p2,p2+(6*N+1));

  double result = 0;
  rep(i,6*N) result += p1[i]*p2[i+1];
  cout << setprecision(10) << result << endl;
  return 0;
}