#include <bits/stdc++.h>
using namespace std;
long long n, t, sum, mx, m, k, a;
double s;
void solve() {
  cin >> n;
  while (n) {
    s += 1. / n;
    n--;
  }
  printf("%.12lf", s);
}
int main() {
  t = 1;
  while (t--) {
    solve();
  }
}
