#include <bits/stdc++.h>
using namespace std;
int xx[4] = {0, 0, 1, -1};
int yy[4] = {-1, 1, 0, 0};
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long int n;
  cin >> n;
  long double sum = 0;
  for (long long int i = 1; i < n + 1; i++) {
    double x = 1.0 / i;
    sum += x;
  }
  cout << fixed << setprecision(12) << sum << "\n";
  return 0;
}
