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

int main() {
  int N, K;
  cin >> N >> K;
  int win = 0;
  random_device rd;
  mt19937 mt(rd());
  for (int i = 1e6; i; i--) {
    int taro = 0;
    int jiro = 0;
    for (int i = 0; i < N; i++) {
      jiro += mt() % 6 + 1;
      if (i < K) taro += mt() % 3 + 4;
      else taro += mt() % 6 + 1;
    }
    if (taro > jiro) win++;
  }
  cout << fixed << setprecision(3) << win / 1e6 << "\n";
}