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

template <typename T, typename U> void cmin(T &a, U b) {
  if (a > b) a = b;
}
template <typename T, typename U> void cmax(T &a, U b) {
  if (a < b) a = b;
}

signed main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);

  random_device rd;
  mt19937 mt(rd());

  long K;
  cin >> K;
  long ans = 0;
  for (long i = 1e6; i; i--) {
    long sum = 0, cnt = 0;
    while (true) {
      sum += mt() % 6 + 1, cnt++;
      if (sum == K) {
        ans += cnt;
        break;
      } else {
        if (sum > K) sum = 0;
      }
    }
  }
  cout << fixed << setprecision(3) << ans / 1e6 << "\n";
}