#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
int A[N];
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int n;
  cin >> n;
  double ans = 1;
  for (double i = 2; i <= n; i++) {
    ans += 1.0 / i;
  }
  cout << setprecision(16) << ans;
  return 0;
}
