#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  long double ans = 0.0;
  for (int deno = 1; deno <= n; deno++) {
    ans += ((1.0) / (deno + 0.0));
  }
  cout << fixed << setprecision(10) << ans;
}
