#include <bits/stdc++.h>
using namespace std;
double add(double s) {
  double ans = 0;
  for (double i = 1.00; i <= s; i++) {
    ans += 1.00 / i;
  }
  return ans;
}
int main() {
  double s;
  cin >> s;
  s = add(s);
  cout << fixed << setprecision(12) << s << endl;
  return 0;
}
