#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

double p[11][64];
double q[11][64];

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

  int n, k;

  cin >> n >> k;
  p[0][0] = q[0][0] = 1.0;

  REP (i, n) {
    REP (j, 64) if (p[i][j] > 0.0) {
      for (int l = 1; l <= 6; l++) {
        p[i+1][j+l] += p[i][j] / 6.0;
      }
    }
  }

  REP (i, n) {
    REP (j, 64) if (q[i][j] > 0.0) {
      if (i < k) {
        for (int l = 4; l <= 6; l++)
          q[i+1][j+l] += q[i][j] / 3.0;
      } else {
        for (int l = 1; l <= 6; l++)
          q[i+1][j+l] += q[i][j] / 6.0;
      }
    }
  }

  double ret = 0;
  REP (i, 64) REP (j, i) ret += q[n][i] * p[n][j];
  cout << fixed << setprecision(12) << ret << endl;
  
  return 0;
}