#include <bits/stdc++.h>
using namespace std;
int main() {
  double n, s, sum = 0;
  scanf("%lf", &n);
  s = n;
  while (s != 0) {
    sum += 1.0 / s;
    s--;
  }
  printf("%.12f\n", sum);
  return 0;
}
