#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  double k = 0;
  for (int i = 0; i < n; i++) {
    k = k + float(1.0 / (n - i));
  }
  cout << fixed << setprecision(15) << k << endl;
}
