#include <bits/stdc++.h>
using namespace std;
int main() {
  double n;
  double rez;
  double fr;
  rez = 0;
  cin >> n;
  for (double i = 1; i <= n; i++) {
    fr = 1.0 / i;
    rez += fr;
  }
  cout << fixed << setprecision(12) << rez << "\n";
  return 0;
}
