#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  double ans = 0.0;
  for (long long i = 1; i <= n; ++i) {
    ans += (1.0) / i;
  }
  cout << setprecision(10) << ans << endl;
  return 0;
}
