#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-8;
const double pi = acos(-1.0);
const long long INF = 0x3f3f3f3f3f3f3f3f;
const int inf = 0x3f3f3f3f;
const int N = 500 + 5;
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  double res = 0;
  for (int i = 1; i <= n; i++) {
    res += 1.0 / i;
  }
  cout << fixed << setprecision(6) << res << endl;
  return 0;
}
