#include <bits/stdc++.h>
using namespace std;
const long long mod = 998244353;
const long long mxi = 2005;
int main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL);
  ;
  long double n;
  cin >> n;
  long double sum = 0;
  while (n != 0) {
    sum += double(1 / n);
    n = n - 1;
  }
  cout << sum << endl;
}
