#include <bits/stdc++.h>
using namespace std;
const long long M = (int)1e9 + 7;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  double res = 0;
  for (int i = 1; i <= n; i++) {
    res += 1.0 / i;
  }
  cout << fixed << setprecision(16) << res;
}
