#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

inline ull xor128() {
  static ull x = 123456789, y = 362436069, z = 521288629, w = 88675123;
  ull t = (x ^ (x << 11));
  x = y, y = z, z = w;
  return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}

int main() {
  auto start = chrono::system_clock::now();
  int n, k;
  cin >> n >> k;
  ull total = 0, win = 0;
  while (true) {
    auto now = chrono::system_clock::now();
    auto diff = chrono::duration_cast<chrono::milliseconds>(now - start).count();
    if (diff > 4500) break;
    ++total;
    int taro = 0, jiro = 0;
    rep(i, n) {
      if (i < k)
        taro += xor128() % 3 + 4;
      else
        taro += xor128() % 6 + 1;
      jiro += xor128() % 6 + 1;
    }
    if (taro > jiro) ++win;
  }
  Debug(win, total);
  cout << fixed << setprecision(15) << (double) win / total << endl;
  return 0;
}