#include <bits/stdc++.h>
using namespace std;
int n;
int main() {
  ios_base ::sync_with_stdio(false), cout.tie(0), cin.tie(0);
  cin >> n;
  double ans = 0;
  for (double i = 1; i <= n; i++) ans += (1 / i);
  cout << ans;
  return 0;
}
