#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9 + 7;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  float ans = 0;
  for (int i = 1; i <= n; i++) {
    float cnt = (float)1 / i;
    ans += cnt;
  }
  cout << ans << endl;
  return 0;
}
