#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void fileIO() {}
int main() {
  fileIO();
  double s;
  cin >> s;
  double ans = 0;
  while (s > 0) {
    ans += (1.0 / s);
    s--;
  }
  cout << fixed << setprecision(12) << ans << endl;
}
