#include <bits/stdc++.h>
using namespace std;
const long long inf = 1e9;
const long long N = 1e5 + 10;
const long long bits = 30;
const long long mod = 1e9 + 7;
const long double pi = 3.14159265358979323846;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  std::cout << std::fixed << std::setprecision(20);
  ;
  long double n;
  cin >> n;
  long double ans = 0;
  for (long double i = 1; i <= n; i++) {
    ans += (long double)1.0 / i;
  }
  cout << ans << "\n";
}
