#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const int mod = 1e9 + 7;
int main() {
  long long n;
  cin >> n;
  double ans = 0;
  for (long long i = 1; i <= n; i++) {
    ans += (double)1 / i;
  }
  printf("%.11f\n", ans);
}
