#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
int n, m, k, mx, t;
string s;
char c;
long long a[1000100];
long double rs = 0;
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) {
    rs += 1.000000 / (n - i + 1);
  }
  cout << rs;
  return 0;
}
