#include <bits/stdc++.h>
using namespace std;
int GCD(int a, int b) { return b == 0 ? a : GCD(b, a % b); }
int lcm(int a, int b) { return (a * b) / GCD(a, b); }
bool isPrime(int n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;
  for (int i = 5; i * i <= n; i = i + 6) {
    if (n % i == 0 || n % (i + 2) == 0) return false;
  }
  return true;
}
int pow(int x, int y, int mod1) {
  int ans = 1;
  for (int i = 1; i <= y; i++) {
    ans = (ans * x) % mod1;
  }
  return ans;
}
signed main() {
  int n;
  cin >> n;
  double ans = 0.0;
  for (double i = 1.0; i <= n; i += 1.0) {
    ans += (double)(1.0 / i);
  }
  cout << fixed << setprecision(6) << ans << endl;
  return 0;
}
