#include <bits/stdc++.h>
using namespace std;
long long a, b, c, d, drag, cnt;
float f, bnt;
string s;
void solve() {
  for (int i = 1; i <= f; ++i) bnt += 1.0 / i;
  cout << fixed << setprecision(11) << bnt;
}
int main() {
  cin >> f;
  solve();
}
