#include <bits/stdc++.h>
using namespace std;
int main() {
  int a;
  cin >> a;
  double ans = 0;
  for (int i = a; i > 0; i--) {
    ans += (double)1 / i;
  }
  cout << fixed << setprecision(6) << ans << endl;
  return 0;
}
