#include <bits/stdc++.h>
using namespace std;
int main(void) {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  int n;
  cin >> n;
  double ans = 0;
  for (int i = 1; i <= n; ++i) ans += 1.0 / i;
  cout << setprecision(12) << fixed << ans << endl;
  return 0;
}
