#include <bits/stdc++.h>
using namespace std;
void err() { std::cerr << '\n' << "END OF DEBUG" << '\n' << '\n'; }
template <typename T, typename... Args>
void err(T a, Args... args) {
  std::cerr << a << ", ";
  err(args...);
}
template <template <typename...> class T, typename t, typename... Args>
void err(T<t> a, Args... args) {
  for (auto x : a) {
    std::cerr << x << ", ";
  }
  err(args...);
}
const long double PI = acos(-1.0);
const long double eps = 1e-6;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
int n;
int main(void) {
  scanf("%d", &n);
  double ans = 0.0;
  for (int i = n; i >= 1; i--) {
    ans += 1.0 / i;
  }
  printf("%.10f\n", ans);
  return 0;
}
