#include <bits/stdc++.h>
using namespace std;
int mpow(int base, int exp);
void solve() {
  long double n;
  cin >> n;
  long double sum = 0;
  while (n) {
    long double d;
    d = (1) * 1.0 / n;
    sum += d;
    n--;
  }
  cout << sum << '\n';
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  solve();
  return 0;
}
int mpow(int base, int exp) {
  base %= 1000000007;
  int result = 1;
  while (exp > 0) {
    if (exp & 1) result = ((long long int)result * base) % 1000000007;
    base = ((long long int)base * base) % 1000000007;
    exp >>= 1;
  }
  return result;
}
