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