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

int main() {
  int K;
  cin >> K;
  random_device rd;
  mt19937 mt(rd());
  int cnt = 0;
  for (int i = 1e6; i; i--) {
    int tmp = 0;
    while (tmp < K) tmp += mt() % 6 + 1, cnt++;
  }
  cout << fixed << setprecision(2) << cnt / 1e6 << "\n";
}