#include <bits/stdc++.h>
const int maxn = 1e3 + 5;
using namespace std;
const long long mod = 1e9 + 7;
const double EPS = 1e-15;
int main() {
  double n;
  cin >> n;
  int up = n;
  double ans = 0.0;
  for (int i = 1; i <= up; ++i) {
    ans += 1.0 / i;
  }
  printf("%.4f\n", ans);
  return 0;
}
