#include <bits/stdc++.h>

using namespace std;

template<typename... Args> class MemoizedRecursion {};

template<typename T> class MemoizedRecursion<T> {
protected:
  vector<bool> use;
  vector<T> mem;

  bool used(int v) {
    if (v >= (int)use.size()) {
      use.resize(v + 1, false);
      mem.resize(v + 1);
    }
    return use[v];
  }

  T memo(int v) {
    return mem[v];
  }

  void push(T t, int v) {
    use[v] = true;
    mem[v] = t;
  }

  virtual T eval(int v) = 0;

public:
  T solve(int v) {
    if (used(v)) return memo(v);
    T t = eval(v);
    push(t, v);
    return t;
  }
};

template<typename T, typename... Args> class MemoizedRecursion<T, Args...> {
protected:
  map<tuple<Args...>, T> mem;

  bool used(Args... args) {
    return mem.count(tie(args...));
  }

  T memo(Args... args) {
    return mem[tie(args...)];
  }

  void push(T t, Args... args) {
    mem[tie(args...)] = t;
  }

  virtual T eval(Args... args) = 0;

public:
  T solve(Args... args) {
    if (used(args...)) return memo(args...);
    T t = eval(args...);
    push(t, args...);
    return t;
  }
};

class Dice : public MemoizedRecursion<double> {
private:
  double eval(int v) {
    double res = 1;
    for (int i = 1; i <= 6; ++i) {
      if (v - i > 0) res += solve(v - i) / 6;
    }
    return res;
  }
};

int main() {
  int k;
  cin >> k;
  Dice dice;
  cout << fixed << setprecision(15) << dice.solve(k) << endl;
}