#include <bits/stdc++.h>
using namespace std;
double sum(long long n) {
  double i, s = 0.0;
  for (i = 1; i <= n; ++i) s = s + 1 / i;
  return s;
}
int main() {
  long long n;
  cin >> n;
  cout << setprecision(12) << sum(n);
  return 0;
}
