#include <bits/stdc++.h>
using namespace std;
int main() {
  cout << setprecision(15) << fixed;
  int n;
  cin >> n;
  double res = 0;
  while (n > 0) {
    res += 1.0 / n;
    n--;
  }
  cout << res << "\n";
  return 0;
}
