#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, s, t = 1;
  double d = 0;
  scanf("%d", &n);
  while (n >= 1) {
    s = n;
    d += ((double)t / s);
    n = s - t;
  }
  printf("%lf", d);
}
