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