#include <bits/stdc++.h>
using namespace std;
int main(void) {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long double n, s = 1.00;
  cin >> n;
  for (long long int i = 2; i <= n; i++) {
    s += (static_cast<long double>(1) / static_cast<long double>(i));
  }
  printf("%0.8Lf", s);
  return 0;
}
