#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  cout << fixed;
  cout << setprecision(12);
  double y = 0.0;
  while (n != 0) {
    double x = 1.0 / n;
    y = y + x;
    n = n - 1;
  }
  cout << y << endl;
  return 0;
}
