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

#define int long long
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define all(x) (x).begin(),(x).end()
#define pb push_back
#define mp make_pair
#define mt make_tuple

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

const int inf = 1LL<<60;
const int mod = 1e9 + 7;
const double eps = 1e-9;

/*{
}*/
vi cnt(61);
vi cnt2(61);
int n, k;

void dfs(int n, int s)
{
  if(n == 0){
    cnt[s]++;
    return;
  }

  rep(i, 6){
    dfs(n-1, s+i+1);
  }
}

void dfs2(int n, int s)
{
  if(n == 0){
    cnt2[s]++;
    return;
  }

  rep(i, 6){
    int t = n <= k and i < 3 ? 3 : 0;
    dfs2(n-1, s+i+1+t);
  }
}

signed main()
{
  cin >> n >> k;

  dfs(n, 0);
  dfs2(n, 0);

  double ans = 0;
  int sum = cnt2[6*n], tmp = pow(6, n);
  for(int i = 6*n-1; i >= n; i--){
//    printf("%lld : %.12f %lld\n", i, ans, sum);
    double t = (double)cnt[i]/tmp; 
    double t2 = (double)sum/tmp;
    ans += t*t2;
    sum += cnt2[i];
  }

  printf("%.12f\n", ans);
  return 0;
}