#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
const int MOD = 1e9 + 7;
const double PI = 2 * acos(0.0);
int main() {
  int n;
  cin >> n;
  double ans = 0;
  for (int i = n; i >= 1; i--) {
    double x = 1.0 / (double)i;
    ans += x;
  }
  cout << fixed << setprecision(10) << ans << endl;
  return 0;
}
