#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double ans = 0;
  scanf("%d", &n);
  for (int i = n; i >= 1; i--) {
    ans = ans + (1.0 / i);
  }
  printf("%.12lf\n", ans);
  return 0;
}
