#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 6;
const long long oo = 1e18 + 9;
const int MOD = 1e9 + 7;
int n;
double sum;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  ;
  cin >> n;
  while (n) {
    sum += double(double(1) / (n--));
  }
  cout << setprecision(6) << fixed << sum << '\n';
}
